10 Mathematics Quarter 4 – Module 5: Using Appropriate Measures of Position and Other Statistical Methods in Analyzing and Interpreting Research Data Department of Education β Republic of the Philippines Mathematics- Grade 10 Alternative Delivery Mode Quarter 4 – Module 5: Uses Appropriate Measures of Position and Other Statistical Methods in Analyzing and Interpreting Research Data First Edition, 2020 Republic Act 8293, section 176 states that: No copyright shall subsist in any work of the Government of the Philippines. However, prior approval of the government agency or office wherein the work is created shall be necessary for exploitation of such work for profit. Such agency or office may, among other things, impose as a condition the payment of royalty. Borrowed materials (i.e., songs, stories, poems, pictures, photos, brand names, trademarks, etc.) included in this book are owned by their respective copyright holders. Every effort has been exerted to locate and seek permission to use these materials from their respective copyright owners. The publisher and authors do not represent nor claim ownership over them. Published by the Department of Education – Division of Bukidnon Secretary: Leonor Magtolis Briones Development Team of the Module Writer: Merlina P. Quita Reviewers: Rhodel A. Lamban, PhD Elbert R. Francisco, PhD Edrix A. Branzuela Rico D. Viernes, MT-II Management Team: Chairperson: Arturo B. Bayocot, PhD, CESO III Regional Director Co-Chairpersons: Victor G. De Gracia Jr. PhD, CESO V Asst. Regional Director Randolph B. Tortola, PhD, CESO IV Schools Division Superintendent Shambaeh A. Usman, PhD Assistant Schools Division Superintendent Mala Epra B. Magnaong, Chief ES, CLMD Neil A. Improgo, PhD, EPS-LRMS Bienvenido U. Tagolimot, Jr., PhD, EPS-ADM Members Elbert R. Francisco, PhD, Chief, CID Rhodel A. Lamban, PhD, EPS Mathematics Rejynne Mary L. Ruiz, PhD, LRMDS Manager Jeny B. Timbal, PDO II Shella O. Bolasco, Division Librarian II Printed in the Philippines by Department of Education – Division of Bukidnon Office Address: Fortich Street, Sumpong, Malaybalay City Telephone: (088) 813-3634 E-mail Address: bukidnon@deped.gov.ph Analyzing and Interpreting Data Using Quartile Lesson 1 What’s New My dear learner, before we start this lesson, let us consider the situation below. Situation: In a class of 30 students, the following are their scores during the 3 rd quarter exam. 55 24 25 40 37 36 20 46 41 39 36 41 45 49 52 24 53 29 31 42 36 56 57 39 44 30 44 25 48 46 The teacher wants to give bonus points to the top 25% of the students, and remedial instruction to the bottom 25% of the students. a. What are the scores of students who will receive bonus points? b. What are the scores of students who will undergo remedial instruction? To answer the questions in the situation above, we have to read and study the discussion of this lesson in the next part. What Is It You learned in the previous modules about the measures of position: quartile, decile, and percentile. When will we use quartile in a situation? Quartile If the situation or problem involves 25% or 50% or 75% of the data, the best measure of position to use is the quartile. In quartiles, the distribution of data is divided into four equal parts. 25% of the distribution are below the 1st quartile (Q1), 50% are below the 2nd quartile (Q2) and 75% are below the 3rd quartile (Q3). This means that 25% of the data has a value Q1, 50% of the data has a value Q2, and 75% of the data has a value Q3. 1 75% 50% 25% Q1 Q2 Middle 50% Bottom 25% Position of quartiles in the distribution Q3 Top 25% Quartiles represent the value for which 25% of the data is below 1 st quartile (Q1) and the value for which 25% of the data is above 3rd quartile (Q3). The bottom 25% of the data has a value of value of > Q3. Q1, and the top 25% of the data has a Quartile of Ungrouped Data To find quartile for ungrouped data, we will solve first its position in the distribution by using the following formula: π Position of πΈπ = (π + π) π where k is 1, 2, or 3 from Q1, Q2, and Q3 n is the total number of data Example: Let us answer the questions in the situation given in What’s New. In a class of 30 students, the following are their scores during the 3 rd quarter exam. 55 40 20 39 45 24 31 56 44 25 24 37 46 36 49 53 42 57 30 48 25 36 41 41 52 29 36 39 44 46 The teacher wants to give bonus points to the top 25% of the students, and remedial instruction to the bottom 25% of the students. a. What are the scores of students who will receive bonus points? b. What are the scores of students who will undergo remedial instruction? Solution: Arrange the data into ascending order. 20 24 24 25 25 29 30 31 36 36 36 37 39 39 40 41 41 42 44 44 45 46 46 48 49 52 53 55 56 57 Since the teacher is looking for the top 25% and bottom 25% of students, we will use quartiles since it involves 25% of the data. This means we are going to find the 1 st quartile (Q1) and 3rd quartile (Q3). 2 Use the following formula to find the position of k th quartile (Qk) π Position of πΈπ = (π + π) π a. The students who will receive bonus points are those students on the top 25% which are the scores above the value of 3 rd quartile (Q3). To find the value of the 3rd quartile, let us follow the following steps. Steps Step 1 Solve for the position of Q3 Figure/ Expression Discussion k Position of Q k = (n + 1) 4 Position of Q3 = Substitute: k with 3 since we are looking for 3rd quartile, and n with 30 (the total number of students or number of data) Perform the addition inside the grouping symbol ( ). (30+1) is 31 3 (30 + 1) 4 3 Position of Q3 = 4 (31) Position of Q3 = Use this formula for the kth quartile 93 4 Multiply 3 and 31 which is equal to 93 Divide 93 by 4 resulting to 23.25. This means, the position of Q3 is between 23rd and 24th data. Position of Q3 = 23.25 20 24 24 25 25 29 30 31 36 36 36 37 39 39 40 41 41 42 44 44 45 46 46 48 49 52 53 55 56 57 23rd 24th Steps Figure/ Expression Step 2 Interpolate the value to obtain the 3rd quartile Discussion Since the result of the position of Q3 is a decimal number, interpolation is needed. Step 2.1 Subtract 23rd data from the 24th data. Step 2.2 Multiply the result in step 2.1 by the decimal part in the position of Q3. Step 2.3 Add the result in step 2.2 to the 23rd data. Look at the arranged data. The 23rd data is 46 and the 24th data is 48. Therefore 48 – 46 = 2 The result in step 2.1 is 2 and the decimal part in the position of Q3 is 0.25 (from 23.25). 2(0.25) = 0.5 46 + 0.5 = 46.5 3rd quartile (Q3) = 46.5 We used 23rd data since the Q3 is between 23rd and 24th data, and the 23rd data is 46. The value of the 3rd quartile is the result of step 2.3. The 3rd quartile here means 75% of the scores are equal or below 46.5. So the scores above 46.5 are the top 25% of the scores. Therefore, the students who will receive bonus points are those students got the scores greater than 46.5. 3 b. The students who will undergo remedial instruction are those students whose scores belong to the bottom 25% which are the scores equal or below the value of 1 st quartile (Q1). To find the value of the 1st quartile, let us follow the following steps Steps Step 1 Solve for the position of Q1 Figure/ Expression k Position of Q k = (n + 1) 4 1 4 Position of Q k = (30 + 1) 1 4 Position of Q k = (31) Position of Q k = 31 4 Position of Q k = 7.75 Discussion Use this formula to find the position of kth quartile Substitute k with 1 since we are looking for 1st quartile, and n with 30 (the total number of students or number of data) Perform the addition inside the grouping symbol ( ). (30+1) is 31. Multiply 1 and 31 which is equal to 31. Divide 31 by 4 resulting to 7.75. This means, the position of Q1 is between 7th and 8th data. 7th 8th 20 24 24 25 25 29 30 31 36 36 36 37 39 39 40 41 41 42 44 44 45 46 46 48 49 52 53 55 56 57 Step 2 Interpolate the value to obtain the 1 st quartile Step 2.1 Subtract 7th data from the 8th data. Step 2.2 Multiply the result in step 2.1 by the decimal part in the position of Q1. Step 2.3 Add the result in step 2.2 to the 7th data. Therefore 31 – 30 = 1 1(0.75) = 0.75 30 + 0.75 = 30.75 1st quartile (Q1) = 30.75 Since the result of the position of Q1 is a decimal number, interpolation is needed. Look at the arrange data. The 7th data 30 and the 8th data is 31. The result in step 2.1 is 1 and the decimal part in the position of Q1 is 0.75 (from 7.75). We used 7th data since the Q1 is between 7th and 8th data, and the 7th data is 30. The value of the 1st quartile is the result of step 2.3. Since the value of the 1st quartile is 30.75, it means 25% of the scores of students are equal or below 30.75. Therefore, the students who will undergo remedial instruction are those students whose scores are equal or below 30.75 . 4 Quartile of Grouped Data To find the quartile of a grouped data, we will be using the following formulae: • First, we have to solve for the class of the quartile using this formula ππ€ ππ₯ππ¬π¬ = Where: • π€π π k is nth quartile, where n = 1, 2, and 3 N is the total frequency Then, use the following formula to find the value of the k th quartile (Qk) π€π − πππ ππ€ = ππ + ( π )π πππ€ Where: LB = lower boundary of the Qk class N = total frequency cfb = cumulative frequency of the class before the Qk class = frequency of the Qk class = size of class interval = nth quartile, where n = 1, 2, and 3 k Example: The table shows the scores of 50 students in a 60-item Mathematics long exam. Scores 56-60 51-55 46-50 41-45 36-40 31-35 26-30 Frequency 4 9 10 9 8 7 3 The passing score of this exam is 45. Is half or 50% of the class passed the exam? Solution: Let us put another columns to our table for the lower boundaries (LB) and the cumulative frequency (cf). Class Interval Scores Frequency (f) 56-60 51-55 46-50 41-45 36-40 31-35 26-30 4 9 10 9 8 7 3 N = 50 Lower Boundaries Less than Cumulative Frequency (LB) (<cf) 55.5 50.5 45.5 40.5 35.5 30.5 25.5 50 46 37 27 18 10 3 5 • How does the Lower Boundaries (LB) computed? The lower boundary of an interval is computed by subtracting 0.5 to the smallest number in the interval. In interval 56-60, the smallest number is 56. Let us use 56 then subtract it by 0.5. So, 56 – 0.5 = 55.5 In interval 51-55, the smallest number is 51. Subtract 51 by 0.5 resulted to 50.5. Class Interval Scores Lower Boundaries (LB) 56-60 51-55 46-50 41-45 36-40 31-35 26-30 55.5 50.5 45.5 40.5 35.5 30.5 25.5 56 – 0.5 = 55.5 51 – 0.5 = 50.5 46 – 0.5 = 45.5 41 – 0.5 = 40.5 36 – 0.5 = 35.5 31 – 0.5 = 30.5 26 – 0.5 = 25.5 a. How does the Cumulative Frequency (cf) computed? The cumulative frequency is the total frequency from the bottom to the current interval. To compute, start from the bottom interval. The cumulative frequency of the bottom interval is equal to its frequency. In the table below, the frequency of the bottom class interval (26-30) is 3, then its cf is also 3. For the next interval (31-35), add the cf of the interval 26-30 to the frequency of the interval 31-35. The frequency of the interval 31-35 is 7. So the cf of this interval is 7 + 3 = 10. For the next intervals, just follow the step where add the frequency of the current interval by the cumulative frequency of the previous interval. Class Interval Scores 56-60 51-55 46-50 41-45 36-40 31-35 26-30 Frequency (f) 4 9 10 9 8 7 3 N = 50 f + 4 9 10 9 8 7 cf before the interval + 46 + 37 + 27 + 18 + 10 + 3 Copy the frequency Less than Cumulative Frequency (<cf) = = = = = = 50 46 37 27 18 10 3 Take note that the cumulative frequency of the top interval is equal to the total frequency (N). 6 If you are done with the table, then let us answer the question: Is half or 50% of the class passed the exam? 50% of the class are the scores equal or below the value of 2 nd quartile. So, to solve for this problem, we are going to compute the 2nd quartile. Steps Step 1 Solve for the Q2 class Figure/ Expression Discussion Use this formula to find the kth quartile class where N is the total frequency. Substitute k with 2 since we are looking for 2nd quartile and N with 50. kN 4 2N 2(50) Q 2 class = = 4 4 100 Q 2 class = 4 Q2 class = 25 Q k class = Multiply 2 and 50 resulting 100. Divide 100 by 4 equals 25. Thus the 2nd quartile (Q2) is the 25th score. This means we need to find the class interval where the 25 th score is contained. Look at the column of cumulative frequency in the table, the 25 th score is within the 19th and 27th scores. Class Interval Scores Frequency (f) Lower Boundaries (LB) 56-60 51-55 46-50 41-45 36-40 31-35 26-30 4 9 10 9 8 7 3 55.5 50.5 45.5 40.5 35.5 30.5 25.5 Less than Cumulative Frequency (<cf) 50 46 37 27 18 10 3 (19th-27th score) (11th-18th score) (4th- 10th score) (1st -3rd score) Q2 Class The 19th -27th scores belong to the class interval 41-45. So, the 25th score is within the class interval 41-45. The Q2 class is the class interval 41-45. After finding the 2nd quartile (Q2) class, we will now solve for the value of the 2 nd quartile (Q2). Steps Step 2 Use the formula to find the value of Q2 Figure/ Expression 2N − cfb Q 2 = LB + ( 4 )π fQ2 25 − 18 Q 2 = 40.5 + ( )5 9 Discussion Where: LB = 40.50 (lower boundary of Q2 class) πππ = 18 (cumulative frequency of the class interval before Q2 class.) ππ 2 = 9 (frequency of Q2 class) π=5 (the size of class intervals) Substitute the values above in the formula. 7 7 Q 2 = 40.5 + ( ) 5 9 25 – 18 is 7. Q 2 = 40.5 + 3.89 7π₯5 ÷ 9 = 3.88888 rounded to 3.89. Q 2 = 44.39 Add 40.5 and 3.89 result to 44.39. Since the value of π2 = 44.39, this means 50% of the students have a score less than or equal to 44.39. Therefore, the 50% of the class did not pass the Mathematics long exam since the passing score is 45. What’s More Let’s practice. 1. The following is the profit of canteen for each food displayed. Foods Sandwich Hotdog Toron Banana Cue Bread Profit 510 505 580 550 510 Foods Puto Cupcake Pizza Siomai Camote Cue Profit 530 505 500 560 535 If the canteen owner wants to reduce 25% of his food display, which of the foods is he going to remove? Answer the following questions. a. What kind of data is this? Grouped or ungrouped? b. What measure of position is appropriate to use in this problem? Quartile, decile, or percentile? c. If the owner want to reduce his food display by 25%, which foods will he remove: the foods at the top 25% of the profit or the foods at the bottom 25% of the profit? Why? d. Arrange the foods according to its profit. If you will use table in arranging the foods, put the food with the highest profit at the top and the food with the lowest profit at the bottom. Foods Profit (food with the highest profit) (food with the lowest profit) e. Solve for the position of 1st quartile (Q1). f. Find the value of the 1st quartile (Q1). g. What are the foods that the canteen owner should remove? 8 2. A barangay captain will sponsor a scholarship program for poor but deserving college students in their barangay. There are 45 applicants for the said scholarship. The selection for the scholar will be based on the family’s monthly income. The captain decided to grant the scholarship to the 25% of the applicant with the lowest family income. Monthly Income (in Pesos) 9,001 – 10,000 8,001 – 9,000 7,001 – 8,000 6,001 – 7,000 5,001 – 6,000 Frequency 7 13 15 7 3 Answer the following questions. a. What kind of data is this? Grouped or ungrouped? b. What measure of position is appropriate to use in this problem? Quartile, decile, or percentile? c. What income would the captain choose, the highest 25% family income of applicants or the lowest 25%? Why? d. Complete the table with lower boundaries and cumulative frequency. e. Solve for the class of 1st quartile (Q1). f. Find the value of the 1st quartile (Q1). g. What are the family income of the student applicants that the barangay captain choose to grant the scholarship? Now check your answer from the answer key at the back. If you got it correctly, then you can proceed to the next lesson. 9 Lesson 2 Analyzing and Interpreting Data Using Decile What’s New My dear learner, before we proceed to our discussion of this lesson, let us explore the following situation. Situation: The table shows the scores of 55 students in a 60-item Mathematics long exam. Scores 56-60 51-55 46-50 41-45 36-40 31-35 26-30 Frequency 5 11 8 7 10 5 9 The passing score of this exam is 45. a. Are all in the bottom 40% of the class failed in the exam? b. Are all in the top 30% of the class passed in the exam? To answer these questions, let us study the discussions that follows. What Is It Decile The deciles are nine score-points which divide a distribution into ten groups. Deciles are denoted as D1, D2, D3,…, D9. They are computed in the same way as the quartiles are calculated. In the figure below, it shows that 10% of the data is less than or equal to the value of D1, 20% of the data is less than or equal to the value of D2, 30% of the data is less than or equal to the value of D3,…, 90% of the data is less than or equal to the value of D 9. When will we use decile in analysing and interpreting data? 10 If the situation or problem is asking for the 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, and 90% of the data, then the appropriate measure of position to be use is decile. If the situation or problem is asking for the top 10% of the data, it means we are looking for the data above the 90% of data or the value of 9th decile (D9). If it is asking for the top 20% of the data, it means we are looking for the data above the 80% of the data or the value of 8 th decile (D8). It follows to other top percentage of data. Decile for Ungrouped Data To find the value of decile, we have to solve first its position in the distribution. Let us use the following formula to solve for the position of decile for ungrouped data. Position of ππ€ = π€ ππ ( π§ + π) where k is 1, 2, 3, …, 9 from D1, D2, …, and D9 n is the total number of data Let’s take this situation. Example: In a class of 40 students, the following are their scores during the 4 th quarter exam. 55 24 25 22 40 37 36 35 20 46 41 39 39 36 41 28 45 49 52 35 24 53 29 42 31 42 36 23 56 57 39 37 44 30 44 37 25 48 46 40 The teacher wants to give bonus points to the top 10% of the students, and remedial instruction to the bottom 20% of the students. Step Step 2 Find the value of D9 Figure/Expression 20 22 23 24 24 25 25 28 29 30 31 35 35 36 36 36 37 37 37 39 39 39 40 40 41 41 42 42 44 44 45 46 46 48 49 52 53 55 56 57 37th Discussion Using the position of 9th decile (D9) which is 37, count the arranged data in ascending order up to the 37th. The 37th score is 53. So, the value of 9th decile (D9) is 53. a. What are the scores of students who will receive bonus points? b. What are the scores of students who will undergo remedial instruction? 11 Solution: Arrange the data into ascending order. 20 22 23 24 24 31 35 35 36 36 39 39 40 40 41 45 46 46 48 49 25 36 41 52 25 37 42 53 28 37 42 55 29 37 44 56 30 39 44 57 Since the teacher is looking for the top 10% and bottom 20% of students, this means we are going to find the 9th decile (D9) and 2nd decile (D2). The 90% of data is less than or equal to the value of 9th decile, and the other 10% of the data (which is the top 10%) are greater than the value of the 9 th decile. Therefore, we will solve for the 9th decile (D9) to find the top 10% of the students’ scores. The 20% of the data is less than or equal to the value of 2nd decile. Therefore, we will solve for the 2nd decile (D2) to find the bottom 20% of the students’ scores. To find the 9th decile (D9) and 2nd decile (D2), we have to solve first its position in the data. Use the following formula to find the position of k th decile (Dk) Position of Dk = k 10 (n + 1) Let us now answer the questions. a. The students who can received a bonus points from the teacher are the students with scores above 90% or above 9th decile (D9). To find the 9th decile, let us find first its position: Step Figure/Expression Step 1 k Solve for Position of Dk = (n + 1) 10 the position of D9 Position of D9 = 9 (40 10 Position of D9 = 9 (41) 10 Position of D9 = 369 10 + 1) Position of D9 = 36.9 or 37 Now let us find the value of the 9th decile. 12 Discussion Use this formula where k is 9 since we are looking for the 9th decile, and n is 40 (the total number of students). Substitute the values of k and n stated above. Perform the addition inside the grouping symbol ( ). (40+1) is 41. Multiply 9 and 41 which is equal to 369. Divide 369 by 10 resulting to 36.9, rounded to 37. Step Step 2 Find the value of D9 Figure/Expression 20 22 23 24 24 25 25 28 29 30 31 35 35 36 36 36 37 37 37 39 39 39 40 40 41 41 42 42 44 44 45 46 46 48 49 52 53 55 56 57 Discussion Using the position of 9th decile (D9) which is 37, count the arranged data in ascending order up to the 37th. The 37th score is 53. So, the value of 9th decile (D9) is 53. 37th Therefore, the students who can received the bonus points are those with scores more than 53. b. The students who will undergo remedial instruction are those with scores below the 2nd decile (D2). To find the value of 2nd decile, let us first solve its position in the arrange data. Step Step 1 Solve for the position of D2 Figure/Expression Position of Dk = Position of D2 = Position of D2 = Position of D2 = k 10 2 10 (n + 1) (40 + 1) 2 10 Discussion Use this formula where k is 2 since we are looking for the 9th decile, and n is 40 (the total number of students). Substitute the values of k and n stated above. Perform the addition inside the grouping symbol ( ). (40+1) is 41. Multiply 2 and 41 which is equal to 82. Divide 82 by 10 resulting to 8.2, rounded to 8. (41) 82 10 Position of π·2 = 8.2 or 8 Now let us find the value of the 2nd decile (D2). Step Figure/Expression Step 2 8th Find the value of D2 20 22 23 24 24 25 25 28 29 30 Discussion Using the position of 2nd decile (D2) which is 8, count the arranged data in ascending order up to the 8th. 31 35 35 36 36 36 37 37 37 39 The 8th score is 28. 39 39 40 40 41 41 42 42 44 44 45 46 46 48 49 52 53 55 56 57 (D2) is 28. So, the value of 2nd decile Therefore, the students who will undergo remedial instruction are those with scores less than or equal to 28. 13 Decile for Grouped Data To find the decile of a grouped data, we will use the following formulae: • First, we have to solve for the class of the decile using this formula. ππ€ ππ₯ππ¬π¬ = Where: • π€π ππ k is the nth decile, where n = 1, 2, 3,…, and 9 N is the total frequency Then, use the following formula to find the value of the k th decile (Dk). π€π − πππ ππ€ = ππ + ( ππ )π πππ€ Where: LB = lower boundary of the Dk class N = total frequency cfb = cumulative frequency of the class before the Dk class fDk = frequency of the Dk class π = size of class interval k = nth decile, where n = 1, 2, 3,…, and 9 Example: Let us answer the situation given in What’s New. The table shows the scores of 55 students in a 60-item Mathematics long exam. Scores 56-60 51-55 46-50 41-45 36-40 31-35 26-30 Frequency 5 11 8 7 10 5 9 The passing score of this exam is 45. a. Are all in the bottom 40% of the class failed in the exam? b. Are all in the top 30% of the class passed in the exam? Solution: Let us add another columns to our table for the lower boundaries and the cumulative frequency. Class Interval Scores Frequency (f) 56-60 51-55 46-50 41-45 36-40 31-35 26-30 5 11 8 7 10 5 9 N = 55 Lower Boundaries (LB) 55.5 50.5 45.5 40.5 35.5 30.5 25.5 14 Less than Cumulative Frequency (<cf) 55 50 39 31 24 14 9 Let us now answer the questions. a. The bottom 40% of the class are those students with scores less than or equal to the value of 4th decile (D4). Let’s find 4th decile (D4) with the following steps. Steps Step 1 Solve for the 4th decile (D4) class Figure/Expression Dk class = kN 10 4(55) 10 220 D4 class = 10 D4 class = 22 D4 class = Discussion Use this formula where k is 4 since we are looking for D4, and N is 55 (total frequency). Substitute k with 4 and N with 55. Multiply 4 and 55 resulting to 220. Divide 220 by 10 is equal to 22. This 4th decile class means that the value of 4th decile is within the interval where 22nd data belong. Let us now look for the class interval where 22nd data belong. D4 class Class Interval Scores Frequency (f) Lower Boundaries (LB) 56-60 5 55.5 Less than Cumulative Frequency (<cf) 55 51-55 11 50.5 50 46-50 8 45.5 39 41-45 7 40.5 31 36-40 10 35.5 24 31-35 5 30.5 14 15th to 24th scores th 10 to 14th 26-30 9 25.5 9 1st to 9th 22nd score belonged N = 55 As you can see above, the 22nd data is within 15th to 24th data and 15th to 24th data belonged to the interval 36-40. We will use this interval as our reference for the formula to find the value of 4 th decile. In the formula, we will use the lower boundary (LB), frequency (f Dk) of the interval and the cumulative frequency before the class interval (cfb). Look again the table above, the encircled numbers are the values of LB, fDk, and cfb. Let us now solve for the value of 4th decile (D4) using the formula kN −cfb Dk = LB + ( 10f Dk )π 15 where k is 4. Step Step 2 Use the formula to find the value of D4 Figure/Expression Discussion Where: LB = 35.5 (lower boundary of D4 class) 4N 4N 10 − cfb 10 cf b D4 = LB + ( )π fD4 fD4 D4 = 35.5 + ( 22−14 )5 10 8 10 40 10 = 22 (the D4 class from step 1) = 14 (cumulative frequency before the class interval of D4) = 10 (Frequency of the class interval) = 5 (Class interval size) Substitute the values above in the formula. D4 = 35.5 + ( ) 5 (22 – 14) is 8. D4 = 35.5 + 8 x 5 = 40 D4 = 35.5 + 4 40 ÷ 10 = 4 D4 = 39.5 35.5 + 4 = 39.5 The value of 4th decile is 39.5. This means that the bottom 40% scores are below or equal to 39.5. Therefore, all the students with scores in the bottom 40% are all failed in the exam since the passing score is 45. b. The top 30% of the class are the scores above the 70% or the 7th decile (D7). Let’s find 7th decile (D7) with the following steps. Steps Step 1 Solve for the 7th decile (D7) class Discussion Figure/Expression Dk class = D7 class = D7 class = ππ 10 7(55) 10 385 10 D7 class = 38.5 Use this formula where k is 7 since we are looking for D7, and N is 55 (total frequency). Substitute k with 7 and N with 55. Multiply 7 and 55 resulting to 385. Divide 385 by 10 is equal to 38.5. This 7th decile class means that the value of 7th decile is within the interval where 38.5th data belong. Let us now look for the class interval where 38.5th data belong. 16 D7 class Class Interval Scores Frequency (f) Lower Boundaries (LB) 56-60 5 55.5 Less than Cumulative Frequency (<cf) 55 51-55 11 50.5 50 46-50 8 45.5 39 41-45 7 40.5 31 36-40 10 35.5 24 31-35 5 30.5 14 25.5 9 26-30 9 N = 55 32nd to 39th scores 38.5th score belonged As you can see in the table, the 38.5th data is within 32nd to 39th data and 32nd to 39th data belonged to the interval 46-50. We will use this interval as our reference for the formula to find the value of 7 th decile. In the formula, we will use the lower boundary (LB), frequency (f Dk) of the interval and the cumulative frequency before the class interval (cfb). Look again the table above, the encircled numbers are the values of LB, fDk, and cfb. Let us now solve for the value of 7th decile (D7) using the formula ππ Dk = LB + ( 10 −πππ ππ·π Step )π where k is 7. Discussion Figure/Expression Step 2 Use the formula to find the value of D7 Where: LB = 45.5 (lower boundary of D7 class) 7π 10 = 38.5 (the D7 class from step 1) πππ = 31 (cumulative frequency before the class interval of D7) ππ·4 = 8 (Frequency of the class interval) π = 5 (Class interval size) 7π D7 = LB + ( 10 −πππ ππ·7 D7 = 45.5 + ( )π 38.5−31 )5 8 7.5 8 37.5 8 Substitute the values above in the formula. 38.5 – 31 = 7.5 D7 = 45.5 + ( ) 5 7.5 x 5 = 37.5 D7 = 45.5 + 37.5 ÷ 8 = 4.69 D7 = 45.5 + 4.69 45.5 + 4.69 = 50.19 The value of 7th decile is 50.19. This means that the scores above 7 th decile or the top 30% are greater than 50.19. Therefore, all students whose scores belong to the top 30% passed the exam. 17 What’s More Let’s practice. 1. The following is the profit of canteen for each food displayed. Foods Sandwich Hotdog Toron Banana Cue Bread Profit 510 505 580 550 510 Foods Puto Cupcake Pizza Siomai Camote Cue Profit 530 505 500 560 535 If the canteen owner wants to increase the capital of the 40% of his food display, which of the foods will he choose? Answer the following questions. a. What kind of data is this? Grouped or ungrouped? b. What measure of position is appropriate to use in this problem? Quartile, decile, or percentile? c. If the owner wants to increase the capital of the 40% of his food display, which foods will he choose: the foods at the top 40% of the profit or the foods at the bottom 40% of the profit? Why? d. Arrange the foods according to its profit. e. Solve for the position of 6th decile (D6). f. Find the value of the 6th decile (D6). g. What are the foods that the canteen owner should increase the capital? 2. A barangay captain will sponsor a scholarship program for poor but deserving college students in their barangay. There are 50 applicants for the said scholarship. The selection for the scholars will be based on their family’s monthly income. The captain decided to grant the scholarship to the 20% of the applicant with the lowest family income. Monthly Income (in Pesos) 9,001 – 10,000 8,001 – 9,000 7,001 – 8,000 6,001 – 7,000 5,001 – 6,000 Frequency 8 13 15 9 5 Answer the following questions. a. What kind of data is this? Grouped or ungrouped? b. What measure of position is appropriate to use in this problem? Quartile, decile, or percentile? c. What income would the captain choose, the highest 20% family income of applicants or the lowest 20%? Why? d. Complete the table with lower boundaries and cumulative frequency. e. Solve for the class of 2nd decile (D2). f. Find the value of the 2nd decile (D2). g. What are the family income of the student applicants that the barangay captain choose to grant the scholarship? 18 Lesson Analyzing and Interpreting Data Using Percentile 3 What’s New My dear learner, before our discussion of this lesson, let us explore the following activities. Situation: In a class of 40 students, the following are their scores during the 1 st quarter exam. 55 24 25 22 40 37 36 35 20 46 41 39 39 36 41 28 45 49 52 35 24 53 29 42 31 42 36 23 56 57 39 37 44 30 44 37 25 48 46 40 The teacher wants to give bonus points to the top 15% of the students, and remedial instruction to the bottom 35% of the students. a. What are the scores of students who will receive bonus points? b. What are the scores of students who will undergo remedial instruction? What Is It Percentile The percentiles are the ninety-nine score points which divide a distribution into one hundred equal parts, so that each part represents the data set. The 1 st percentile (P1) separates the lowest 1% from the other 99%, the 2nd percentile (P2) separates the lowest 2% from the other 98%, and so on. P25 Q1 P10 D1 P20 D2 P50 Q2 P30 D3 P40 D4 P50 D5 P75 Q3 P60 D6 P70 D7 P80 D8 P90 D9 The percentiles determine the value for 1%, 2%,…, and 99% of the data. P 20 or 20th percentile of the data means 20% of the data have values less than or equal to P20. The 1st quartile is the 25th percentile. It means 25% of the data is less than or equal to the value of P25 or Q1. The 1st decile is the 10th percentile. It means 10% of the data is less than or equal to the value of P10 or D1, and so on. 19 Percentile for Ungrouped Data Here is how to find percentile for ungrouped data. We will solve first its position by using the following formula: Position of ππ€ = π€ πππ (π§ + π) where k is 1, 2, 3, …, 99 from P1, P2, …, and P99 n is the total number of data Example: In a class of 40 students, the following are their scores during the 1 st quarter exam. 55 24 25 22 40 37 36 35 20 46 41 39 39 36 41 28 45 49 52 35 24 53 29 42 31 42 36 23 56 57 39 37 44 30 44 37 25 48 46 40 The teacher wants to give bonus points to the top 15% of the students, and remedial instruction to the bottom 35% of the students. a. What are the scores of students who will receive bonus points? b. What are the scores of students who will undergo remedial instruction? Solution: Arrange the data into ascending order. 20 22 23 24 24 31 35 35 36 36 39 39 40 40 41 45 46 46 48 49 25 36 41 52 25 37 42 53 28 37 42 55 29 37 44 56 30 39 44 57 Since the teacher is looking for the top 15% and bottom 35% of students, this means we are going to find the 85th percentile (P85) and 35th percentile (P35). The 85% of data is less than or equal to the value of 85 th percentile, and the other 15% of the data (which is the top 15%) are greater than the value of the 85 th percentile. Therefore, we will solve for the 85th percentile (P85) to find the top 15% of the students’ scores. The 35% of the data is less than or equal to the value of 35th percentile. Therefore, we will solve for the 35th percentile (P35) to find the bottom 35% of the students’ scores. To find the 85th percentile (P85) and 35th percentile (P35), we have to solve first its position in the data. Use the following formula to find the position of k th percentile (Pk) Position of Pk = k 100 (n + 1) Let us now answer the questions. a. The students who can received a bonus points from the teacher are the students with scores above 85% or 85th percentile (P85). 20 To find the 85th percentile (P85), let us first find its position: Step Figure/Expression Step 1 Solve for k Position of Pk = (n + 1) the 100 position of P85 Position of P85 = 85 (40 100 Position of P85 = 85 (41) 100 Position of P85 = 3485 100 Discussion Use this formula where k is 85 since we are looking for the 85th percentile, and n is 40 (the total number of students). Substitute the values of k and n stated above. Perform the addition inside the grouping symbol ( ). (40+1) is 41. Multiply 85 and 41 which is equal to 3485. Divide 3485 by 100 resulting to 34.85, rounded to 35. + 1) Position of P85 = 34.85 or 35 Now let us find the value of the 85th percentile. Step Step 2 Find the value of P85 Figure/Expression 20 22 23 24 24 25 25 28 29 30 31 35 35 36 36 36 37 37 37 39 39 39 40 40 41 41 42 42 44 44 45 46 46 48 49 52 53 55 56 57 35th Discussion Using the position of 85th percentile (P85) which is 35, count the arranged data in ascending order up to the 35th. The 35th score is 49. So, the value of 85th percentile (P85) is 49. Therefore, the students who can received the bonus points are those with scores greater than 49. The scores are 52,53,55,56 and 57. b. The students who will undergo remedial instruction are those with scores below the 35th percentile (P35). To find the value of 35th percentile (P35), let us first solve its position in the arrange data. Step Step 1 Solve for the position of P35 Figure/Expression Position of ππ = π (π 100 Position of π35 = Position of π35 = Position of π35 = 35 100 + 1) (40 + 1) 35 (41) 100 1435 100 Position of π35 = 14.35 or 14 Discussion Use this formula where k is 35 since we are looking for the 35th percentile, and n is 40 (the total number of students). Substitute the values of k and n stated above. Perform the addition inside the grouping symbol ( ). (40+1) is 41. Multiply 35 and 41 which is equal to 1435. Divide 1435 by 100 resulting to 14.35, rounded to 14. 21 Now let us find the value of the 35th percentile (P35). Step Step 2 Find the value of P35 Figure/Expression 20 22 23 24 24 25 25 28 29 30 31 35 35 36 36 36 37 37 37 39 Discussion Using the position of 35th percentile (P35) which is 14, count the arranged data in ascending order up to the 14th. 39 39 40 40 41 41 42 42 44 44 The 14th score is 36. 45 46 46 48 49 52 53 55 56 57 So, the value of 35th percentile (P35) is 36. 14th Therefore, the students who will undergo remedial instruction are those with scores less than or equal to 36 that is, students with scores of 20,22,23,24,25,28,29,30,31,35,and 36. Percentile for Grouped Data To find the percentile of a grouped data, we will use the following formulae: • First, we have to solve for the class of the percentile using this formula. Pk class = Where: • π€π πππ k is the nth percentile, where n = 1, 2, 3,…, and 99 N is the total frequency Then, use the following formula to find the value of the kth percentile (Pk). π€π −πππ πππ Pk = LB + ( Where: LB = lower boundary of the Pk class N = total frequency cfb = cumulative frequency of the class before the Pk class πππ€ )π’ ππ π = frequency of the Pk class π = size of class interval π = nth percentile, where n = 1, 2, 3,…, and 99 Example: The table shows the scores of 55 students in a 60-item Mathematics long exam. Scores 56-60 51-55 46-50 41-45 36-40 31-35 26-30 Frequency 5 11 8 7 10 5 9 The passing score of this exam is 45. 22 a. Are all in the bottom 45% of the class failed in the exam? Solution: Let us put another columns to our table for the lower boundaries and the cumulative frequency. Class Interval Scores Frequency (f) Lower Boundaries (LB) Less than Cumulative Frequency (<cf) 56-60 51-55 46-50 41-45 36-40 31-35 26-30 5 11 8 7 10 5 9 55.5 50.5 45.5 40.5 35.5 30.5 25.5 55 50 39 31 24 14 9 N = 55 Let us now answer the questions. a. The bottom 45% of the class are those students with scores less than or equal to the value of 45th percentile (P45). Let’s find 45th percentile (P45) with the following steps. Steps Step 1 Solve for the 45th percentile (P45) class Discussion Figure/Expression Pk class = kN 100 P45 class = P45 class = 45(55) 100 2475 100 P45 class = 24.75 Use this formula where k is 45 since we are looking for P45, and N is 55 (total frequency). Substitute k with 45 and N with 55. Multiply 45 and 55 resulting to 2475. Divide 2475 by 100 is equal to 24.75. This 45th percentile class means that the value of 45th percentile is within the interval where 24.75th data belong. Let us now look for the class interval where 24.75 th data belong. Since 24.75th is in the boundary between 24th and 25th, then let us round off 24.75 to 25. Now, 45 th percentile belongs to the interval 41-45. 23 P45 class Class Interval Scores Frequency (f) Lower Boundaries (LB) 56-60 5 55.5 Less than Cumulative Frequency (<cf) 55 51-55 11 50.5 50 46-50 8 39 41-45 7 45.5 40.5 36-40 31-35 10 5 35.5 30.5 24 14 25th to 31st scores 15th to 24th 10th to 14th 26-30 9 N = 55 25.5 9 1st to 9th 31 25th score belonged We will use this interval as our reference for the formula to find the value of 45 th percentile. In the formula, we will use the lower boundary (LB), frequency (f Pk) of the interval and the cumulative frequency before the class interval (cf b). Look again the table above, the encircled numbers are the values of LB, fPk, and cfb. Let us now solve for the value of 45th percentile (P45) using the formula kN −cfb Pk = LB + (100 fPk Step Step 2 Use the formula to find the value of P45 )i where k is 45. Discussion Figure/Expression 45N P45 = LB + ( 100 −cfb fP45 )i Where: LB = 40.5 (lower boundary of D4 class) 45π 100 = 24.75 (the P45 class from step 1) πππ = 24 (cumulative frequency before the class interval of P45) ππ45 = 7 (Frequency of the class interval) π = 5 (Class interval size) P45 = 40.5 + 24.75−24 ( )5 7 P45 = 40.5 + ( P45 = 40.5 + 0.75 )5 7 3.75 7 Substitute the values above in the formula. (24.75 – 24) is 0.75. 0.75 x 5 = 3.75 P45 = 40.5 + 0.54 3.75 ÷ 7 = 0.54 P45 = 41.04 40.5 + 0.54 = 41.04 The value of 45th percentile is 41.04. This means that the bottom 45% scores are below or equal to 41.04. Therefore, all the students with scores in the bottom 45% are all failed in the exam since the passing score is 45. 24 What’s More Let’s practice. 1. The following is the profit of canteen for each food displayed. Foods Sandwich Hotdog Toron Banana Cue Bread Profit 510 505 580 550 510 Foods Puto Cupcake Pizza Siomai Camote Cue Profit 530 505 500 560 535 If the canteen owner wants to reduce 15% of his food display, which of the foods is he going to remove? Answer the following questions. a. What kind of data is this? Grouped or ungrouped? b. What measure of position is appropriate to use in this problem? Quartile, decile, or percentile? c. If the owner want to reduce his food display by 15%, which foods will he remove: the foods at the top 15% of the profit or the foods at the bottom 15% of the profit? Why? d. Arrange the foods according to its profit. e. Solve for the position of 15th percentile (P15). f. Find the value of the 15th percentile (P15). g. What are the foods that the canteen owner should remove? 2. A barangay captain will sponsor a scholarship program for poor but deserving college students in their barangay. There are 50 applicants for the said scholarship. The selection for the scholar will be based on the family’s monthly income and their grades. The captain decided to reduce his choices by removing 55% of the applicants based on their family income. What family income of the student applicants would the captain remove from his choices of scholarship? Monthly Income (in Pesos) 9,001 – 10,000 8,001 – 9,000 7,001 – 8,000 6,001 – 7,000 5,001 – 6,000 Frequency 8 13 15 9 5 Answer the following questions. a. What kind of data is this? Grouped or ungrouped? b. What measure of position is appropriate to use in this problem? Quartile, decile, or percentile? c. What income would the captain choose, the highest 55% family income of applicants or the lowest 55%? Why? d. Complete the table with lower boundaries and cumulative frequency. e. Solve for the class of 45th percentile (P45). f. Find the value of the 45th percentile (P45). g. What are the family income of the student applicants that the barangay captain choose to remove from his choices of scholarship? 25 What I Have Learned Let’s see what you have learned by completing the statements below providing the missing word(s), phrase, or figures. In quartile, the distribution of data is divided into (1.)_______ equal parts. 25% of the data has a value (2.)_______, (3.)_______ of the data has a value ≤ Q2, and 75% of the data has a value ≤ Q3. The value at the bottom 25% of the data is below (4.)_______ and the value at the top (5.)_______ of the data is above the 3rd quartile. In decile, the distribution of data is divided into 10 equal parts. 10% of the data has a value ≤ D1, (6.)_______ of the data has a value ≤ D2, 30% of the data has a value (7.)_______, …, and (8.)_______ of the data has a value ≤ D 9. The value at the bottom 20% of the data is below (9.)_______, and the value at the top 10% of the data is (10.)_______ the 9th decile. In percentile, the distribution of data is divided into 100 equal parts. 10% of the data has a value ≤ P10, (11.)_______ of the data has a value ≤ P 37, 68% of the data has a value (12.)_______, …, and (13.)_______ of the data has a value ≤ P 99. The value at the bottom 20% of the data is below (14.)_______ percentile, and the value at the top (15.)_______ of the data is above the 85th percentile. What I Can Do Collect data about the height of your 15 friends. Present it using a frequency table. Identify the height of the 10% tallest among your friends, then list down their names. Assessment Choose the letter of the best answer. 1. Which of the following measures of position is appropriate to use if we are looking for the 75% of the data? A. quartile B. percentile C. decile D. percentile rank 2. Which of the following measures of position is appropriate to use if we are looking for the 80% of the data? A. quartile B. percentile C. decile D. percentile rank 3. Which of the following measures of position is appropriate to use if we are looking for the 33% of the data? A. quartile B. percentile C. decile D. percentile rank 4. What percent of the data is above the 7 th decile? A. 3% B. 7% C. 30% 26 D. 70% The school principal of Malipayon High School surveyed the ages of his 40 teachers. These are the data he collected: 36 42 31 37 32 25 31 51 24 24 46 50 50 37 44 23 43 42 35 49 45 52 44 39 30 46 31 46 27 39 42 45 5. What are the ages of teachers in the bottom 13%? A. ≤ 13 B. ≤ 25 C. ≤ 30 D. ≤ 31 6. What are the ages of teachers in the bottom 30%? A. ≤ 25 B. ≤ 30 C. ≤ 31 D. ≤ 70 7. What are the ages of teachers in the bottom 25%? A. ≤ 25 B. ≤ 30 C. ≤ 31 D. ≤ 75 23 28 31 27 32 28 39 35 8. What measure of position is appropriate in finding the ages in the bottom 25%? A. quartile B. percentile C. decile D. percentile rank 9. What are the ages of teachers in the top 10%? A. > 24 B. > 42 C. > 45 D. > 50 10. What are the ages of teachers in the top 25%? A. > 30 B. > 42 C. > 45 D. > 50 11. What are the ages of teachers in the top 35%? A. > 31 B. > 42 C. > 45 D. > 50 A teacher surveyed the distances of her students’ house from school in kilometres. The data she collected from 35 students is presented in a frequency table below. Class interval ( distances from school to Frequency( No. of students) students’ house in km) 12 – 14 5 9 – 11 3 6 –8 8 3–5 9 0–2 10 12. How far are the top 20% of the students’ house from school? A. > 4.42 km B. > 9.5 km C. > 8.22 km D. > 11.25 km 13. How far are the top 25% of the students’ house from school? A. > 4.42 km B. > 9.5 km C. > 8.22 km D. > 11.25 km 14. How far are the top 15% of the students’ house from school? A. > 4.42 km B. > 9.5 km C. > 8.22 km D. > 11.25 km 15. How near are the bottom 45% of the students’ house from school? A. ≤ 4.42 km B. ≤ 9.5 km C. ≤ 8.22 km D. ≤ 11.25 km 27 28 Lesson 2: What’s More Lesson 2: What’s More 2. a. b. c. d. 1. Grouped Decile Lowest 20% Monthly Income Frequency (in Pesos) e. f. g. 5 5,001 – 6,000 9 6,001 – 7,000 15 7,001 – 8,000 13 8,001 – 9,000 8 9,001 – 10,000 a. Ungrouped b. Decile c. Top 40% d. LB Foods Toron Siomai Banana Cue Camote Cue Puto Sandwich Bread Hotdog Cupcake Pizza <cf 5 5000.5 14 6000.5 29 7000.5 42 8000.5 50 9000.5 D2 Class= 10 D2 = 6556.056 The family income which is less than or equal to Php6,556.06. e. f. g. Lesson 1: What’s More Lesson 1: What’s More 2. a. b. c. d. Profit 580 560 550 535 530 510 510 505 505 500 Position of D6= 6.6 or 7 D6= 535 Banana Cue, Siomai, and Toron What’s More 1. Grouped Quartile Lowest 25% a. Ungrouped b. Quartile c. Bottom 25% d. Monthly Income Frequency (in Pesos) e. f. g. Lesson 2 3 5,001 – 6,000 7 6,001 – 7,000 15 7,001 – 8,000 13 8,001 – 9,000 7 9,001 – 10,000 LB Foods Toron Siomai Banana Cue Camote Cue Puto Sandwich Bread Hotdog Cupcake Pizza <cf 3 5000.5 10 6000.5 25 7000.5 38 8000.5 45 9000.5 Q1 Class= 11.25 Q1 =7083.83 The family income which is less than or equal to Php7,083.83. e. f. g. Profit 580 560 550 535 530 510 510 505 505 500 Position of Q1=2.75 or 3 Q1=505 Pizza, Cupcake, and Hotdog Lesson 1 What’s More Key to Answers 29 Assessment B 5. C 4. B 3. C 2. A 1. 15. A 10. C 14. D D 9. A 8. B 7. C 6. 11. B 12. B What I Have Learned 25% 5. 1st quartile 4. 8. 50% 3. 7. ≤ Q1 2. 4 1. 6. 9. 14. 20th Percentile 2nd decile 13. 99% 90% 12. ≤ P68 ≤ D3 11. 37% 20% 10. above 15. 15% Lesson 3: What’s More Lesson 3: What’s More 2. a. b. c. d. 1. Grouped Decile Highest 55% a. Ungrouped b. Percentile c. Bottom 15% d. Monthly Income Frequency (in Pesos) e. f. g. 13. C Assessment What I Have Learned 5 5,001 – 6,000 9 6,001 – 7,000 15 7,001 – 8,000 13 8,001 – 9,000 8 9,001 – 10,000 LB Foods Toron Siomai Banana Cue Camote Cue Puto Sandwich Bread Hotdog Cupcake Pizza <cf 5 5000.5 14 6000.5 29 7000.5 42 8000.5 50 9000.5 P45 Class= 22.5 P45 = 7567.167 The family income which is greater than Php7,567.17. e. f. g. Profit 580 560 550 535 530 510 510 505 505 500 Position of P15= 1.65 or 2 P15= 505 Pizza, Cupcake, and Hotdog Lesson 3 What’s More References Callanta, Melvin, Canonigo, Allan, Chua, Arnaldo, Cruz, Jerry, Esparrago, Mirla, Garcia, Elino, Magnaye, Aries, Orines, Fernando, Perez, Rowena, and Ternida, Concepcion. 2015. Mathematics 10 Learners Module. Philippines: Rex Bookstore, Inc. Dilao, Soledad, Orines, Fernando, and Bernabe, Julieta. 2009. Advance Algebra, Trigonometry and Statistics. Quezon City: SD Publications, Inc. Malaborbor, Pastor, Sabangan, Leticia, Carreon, Editha, and Lorenzo, Jose Ramon. 2003. Functions. Metro Manila: Diamond Offset Press, Inc. Milefoot.com Mathematics. “Measures of Position”.http://www.milefoot.com/math/stat/desc-positions.htm Universal Class. “How to Determine Measures of Position”. https://www.universalclass.com/articles/math/statistics/measures-of-positionpercentiles-quartiles.htm For inquiries and feedback, please write or call: Department of Education –Learning Resources Management and Development Center(LRMDC) DepEd Division of Bukidnon Sumpong, Malaybalay City, Bukidnon Telefax: ((08822)855-0048 E-mail Address: bukidnon@deped.gov.ph 30