Statistics and Probability Quarter 3 – Module 8: Length of Confidence Interval and Appropriate Sample Size ` Statistics and Probability Alternative Delivery Mode Quarter 3 – Module 8: Length of Confidence Interval and Appropriate Sample Size 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 royalties. Borrowed materials (i.e., songs, stories, poems, pictures, photos, brand names, trademarks, etc.) included in this module 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 Secretary: Leonor Magtolis Briones Undersecretary: Diosdado M. San Antonio SENIOR HS MODULE DEVELOPMENT TEAM Author Co-Author – Language Editor Co-Author – Content Evaluator Co-Author – Illustrator Co-Author – Layout Artist : Darwin Rex N. Mallari : Nina S. Manuel : Regina M. Poli : Rona E. Mallari : Nathaniel C. Sebastian Team Leaders: School Head LRMDS Coordinator : Reycor E. Sacdalan PhD : Pearly V. Villagracia SDO-BATAAN MANAGEMENT TEAM: Schools Division Superintendent OIC- Asst. Schools Division Superintendent Chief Education Supervisor, CID Education Program Supervisor, LRMDS Education Program Supervisor, AP/ADM Education Program Supervisor, Senior HS Project Development Officer II, LRMDS Division Librarian II, LRMDS : Romeo M. Alip, PhD, CESO V : William Roderick R. Fallorin, CESE : Milagros M. Peñaflor, PhD : Edgar E. Garcia, MITE : Romeo M. Layug : Danilo C. Caysido : Joan T. Briz : Rosita P. Serrano REGIONAL OFFICE 3 MANAGEMENT TEAM: Regional Director Chief Education Supervisor, CLMD Education Program Supervisor, LRMS Education Program Supervisor, ADM : May B. Eclar, PhD, CESO III : Librada M. Rubio, PhD : Ma. Editha R. Caparas, EdD : Nestor P. Nuesca, EdD Statistics and Probability Quarter 3 – Module 8: Length of Confidence Interval and Appropriate Sample Size Introductory Message This Self-Learning Module (SLM) is prepared so that you, our dear learners, can continue your studies and learn while at home. Activities, questions, directions, exercises, and discussions are carefully stated for you to understand each lesson. Each SLM is composed of different parts. Each part shall guide you step-bystep as you discover and understand the lesson prepared for you. Pre-tests are provided to measure your prior knowledge on lessons in each SLM. This will tell you if you need to proceed on completing this module or if you need to ask your facilitator or your teacher’s assistance for better understanding of the lesson. At the end of each module, you need to answer the post-test to self-check your learning. Answer keys are provided for each activity and test. We trust that you will be honest in using these. In addition to the material in the main text, Notes to the Teacher are also provided to our facilitators and parents for strategies and reminders on how they can best help you on your home-based learning. Please use this module with care. Do not put unnecessary marks on any part of this SLM. Use a separate sheet of paper in answering the exercises and tests. And read the instructions carefully before performing each task. If you have any questions in using this SLM or any difficulty in answering the tasks in this module, do not hesitate to consult your teacher or facilitator. Thank you. What I Need to Know At the end of the lesson, the learner should be able to: ➢ Identify the length of a confidence interval. (M11/12SP-IIIj-1) ➢ Compute for the length of the confidence interval. (M11/12SP-IIIj-2) ➢ Compute for an appropriate sample size using the length of interval. (M11/12SP-IIIj-3) ➢ Solve exercise involving sample size determination. (M11/12SP-IIIj-4) . What I Know A. Find the length of the following confidence interval. 1. 0.0254 < p < 0.560 2. 0.385< p < 0.655 3. 0.363 < p < 0.655 4. Upper confidence limit = 0.632 Lower confidence limit = 0.475 5. Upper confidence limit = 0.686 Lower confidence limit = 0.415 B. Find the length of the confidence interval given the following data: 6. 𝑠 = 8.47, n = 300, confidence level= 95% 7. 𝑠 = 6.25, n = 150, confidence level= 95% 8. 𝑠 = 4.36, n = 350, confidence level= 99% 9. s = 5.25, n = 16, confidence interval = 95% 10. s = 7.15, n = 20, confidence interval= 99% 1 Lesson 1 Length of Confidence and Appropriate Sample Size How large should be the sample? Many researchers find this a problem. In fact, many rely on old methods to determine the sample size they need in their investigations. This problem must be addressed carefully because needlessly large samples are a waste of important resources. On the other hand, insufficient sample size may lead to poor results. What’s In A. Fill in the blank with the correct word or group of words to make a meaningful statement. Write your answer on a separate sheet of paper. 1. Statistically, rounding up of 111.12 is____________________. 2. A confidence level is the confidence coefficient and is expressed as __________________. 3. For a 95% confidence level, the confidence coefficient is __________________. 4. When a 99% confidence level is selected, a = _______________. 5. The standard deviation of a sampling distribution is called _____________. 6. A subset of the interest population is called ______________. B. Answer the following: 1. 1 – 0.38 2. (0.35) (0.65) 3. 1.96(2) 0.06 4. ( 5. ( (1.96)(5.3) 2 0.2 ) (2.58)(2.5) 2 0.10 ) 2 Note to the Teacher In this module, the learners will be able to know how to compute for the length of the confidence interval and for an appropriate sample size needed using the length of interval. What’s New Definition of Terms 1. Confidence interval - In statistics, this refers to the probability that a Population parameter will fall between a set of values for a certain proportion of times. Confidence intervals measure the degree of uncertainty or certainty in a sampling method. They can take any number of probability limits, with the most common being a 95% or 99% confidence level. 2. Narrowness of the interval – This pertains to a small width in relation to the length of the confidence interval. Length of Confidence Interval This refers to the absolute difference between the upper confidence limit and the lower confidence limit. Formula: LCI = |UCL – LCL| = |LCL – UCL| Or LCI = UCL – LCL Where: LCI – length of confidence interval UCL – upper confidence limit LCL – lower confidence limit 3 Example 1. Find the length of the confidence interval 0. 275<p<0.360 Solution: Steps 1. Determine the given. Solution UCL = 0.360 LCL = 0.275 LCl = UCL – LCL 2. Use the formula for Length of Confidence Interval. 3. Substitute the given value, then perform the indicated operation. LCI = 0.360 - 0.275 LCI = 0.085 Thus, the length of confidence is 0.085. Example 2. Find the length of the confidence interval upper confidence limit = 0.805 lower confidence limit = 0.526 Solution: Steps 1. Determine the given. Solution UCL = 0.805 LCL = 0.526 LCl = UCL – LCL 2. Use the formula for Length of Confidence Interval. 3. Substitute the given value, then perform the indicated operation. LCI = 0.805 - 0.526 LCI = 0.279 Thus, the length of confidence interval is equal to 0.279. Try this in your notebook. A. Find the length of the confidence interval. 1. 0.355 < p < 0.470 2. 0.475 < p < 0.835 3. Upper confidence limit = 0.796 Lower confidence limit = 0.536 4. Upper confidence limit = 0.896 Lower confidence limit = 0.526 5. Upper confidence limit = 0.966 Lower confidence limit = 0.635 4 What is It The formula for interval estimate of population mean (µ) with known variance is: ̅ − 𝒛𝒂⁄𝟐 𝒙 𝝈 √𝒏 ̅ − 𝒛𝒂⁄ <𝒖<𝒙 𝟐 𝝈 √𝒏 The formula to find the length of the confidence interval = 𝟐𝒛𝒂⁄ 𝟐 𝝈 √𝒏 Where: 𝒛𝒂⁄ – is the z value 𝟐 𝝈 – standard deviation 𝒏 – sample size Example 3: Find the length of the confidence interval given the following data: = 0.3, 𝑛=70, confidence level=95% Solution: Steps 1. Determine the given. 2. Determine the confidence coefficient. Solution = 0.3, n =70, confidence level=95% (1- 𝑎)100% = 95% Find 𝑎 in equation (1𝑎)100% = 95% where in 95% is the given confidence level. (1- 𝑎) = 95% 100% of (1 - 𝑎) = (1 - 𝑎) (1- 𝑎 )= 0.95 Charge 95% to decimal number. (1- 𝑎) - 1 = 0.95 -1 Subtraction property of equality. (-1)(-𝑎) = (-0.05)(-1) Multiplication property of 𝒂 = 0.05 equality. 𝑎/2 = 0.05/2 𝒂/𝟐 = 0.025 5 Division property of equality. 0.500 - 0.025 = 0.475 𝒛𝒂⁄ = 1.96 𝟐 3. Substitute the values in the formula and compute. 𝝈 LCl = 𝟐𝒛𝒂⁄ . 𝟐 √𝒏 𝒔 𝟐 √𝒏 LCl = 𝟐𝒛𝒂⁄ . LCl = 𝟐(1.96) ( LCl = 0.3 ) √70 1.176 √70 Subtract 0.025 from 0.500 (which is half the area of the Standard Normal Curve). Hence, Using the Area under the Standard Normal Curve Table, as 𝑠ℎ𝑜𝑤𝑛 𝑏𝑒𝑙𝑜𝑤. Use this formula to solve for the length of confidence interval. Supplies the values, then multiply 2(1.96)(0.3). Divide 1.176 by √60. LCI = 0.1406 Answer Thus, the length of confidence interval is equal to 0.1406 Try this in your notebook. B. Find the length of the confidence interval given the following data: 1. = 0.3, n = 45, confidence level 98% 6 2. = 0.5, n = 50, confidence level 95% 3. = 1.5, n = 70, confidence level 99% The formula for confidence interval of population mean, if n<30 𝝈 2 √𝑛 𝑥̅ − 𝑡𝑎⁄ < µ < 𝑥̅ − 𝑡𝑎/2 𝝈 √𝑛 The formula to find the length of the confidence interval. 𝝈 2 √𝑛 LCl = 2𝑡𝑎⁄ Where: 𝒕𝒂⁄ – is the t value 𝟐 𝝈 – standard deviation 𝒏 – sample size Example 4: Find the length of the confidence interval, given the following data: s = 6.5, n= 15, confidence level = 99% Solution: Steps 1. Determine the given. 2. Find the degree of freedom df. 3. Find the 𝒂 in (1𝑎)100% confidence level, then find 𝒕𝒂⁄ Solution s = 6.5, n= 15, confidence level = 99% df = n-1 df = 15-1 df = 14 Thus, the degree of freedom is 14. (1- 𝑎)100% = 99% 𝟐 Find 𝑎 in equation (1𝑎)100% = 99% where in 99% is the given confidence level (1- 𝑎) = 99% Since, 100% of (1 – 𝑎) is equal to (1 - 𝑎) (1- 𝑎 )= 0.99 Charge 99% to decimal number (1- 𝑎) - 1 = 0.99 -1 Subtraction property of equality. 7 (-1)(-𝑎) = (-0.01)(-1) a = 0.01 Division property of equality. 𝑎/2 = 0.01/2 𝒂/𝟐= 0.005 Hence, Using the t distribution critical values (t Table) at df = 14 and 𝑎⁄ = 0.005 , as 𝑠ℎ𝑜𝑤𝑛 𝑏𝑒𝑙𝑜𝑤. 2 𝒕𝒂⁄ = 2.977 𝟐 4. Substitute the values in the formula and compute. LCl = 𝟐𝒕𝒂⁄ . LCl = 𝟐𝒕𝒂⁄ . Multiplication property of equality. 𝒔 Use this formula to solve for the length of confidence interval. 𝟐 √𝒏 𝝈 𝟐 √𝒏 LCl = 𝟐(2.977) ( LCl = 38.701 √15 6.5 ) √15 Supplies the values, then multiply 2(2.977) (6.5). Divide 38.701 by √15. LCI = 9.99 Answer Thus, the length of confidence interval is equal to 9.99 8 Try this: C. Find the length of the confidence interval given the following data: 1. s = 4.5, n = 20, confidence interval = 98% 2. s = 3.5, n = 25, confidence interval = 95% 3. s = 2.5, n = 28, confidence interval = 99% Deriving the Formula for a Sample Size In deriving the formula for the sample size, there are two things to remember when we decided on the quality of the sample size that we need: confidence and the narrowness of the interval. ➢ Confidence interval describes the uncertainty inherent in this estimate and describes a range of values within which we can be reasonably sure that the true effect actually lies. ➢ Narrowness of the interval pertains to a small width in relation to the length of the confidence interval. If the confidence interval is relatively narrow (e.g., 0.70 to 0.80), the effect size is known precisely. If the interval is wider (e.g., 0.60 to 0.93) the uncertainty is greater, although there may still be enough precision to make decisions about the utility of the intervention. Intervals that are very wide (e.g., 0.50 to 1.10) indicate that we have little knowledge about the effect, and that further information is needed. The computing formula in determining sample size is derived from the formula of the margin of error E where: 𝐸= • • 𝜎 𝑧𝑎 ⁄2 ( ) √𝑛 Study the derivation of the computing formula for determining minimum sample size when estimating a population mean. Discuss the elements of the formula. To solve for n, which is a sample size needed in estimating a population mean, do this. (Hint: Apply the appropriate properties of equality.) 𝐸= 𝑧𝑎/2 ⋅ 𝜎 Formula for margin of error. √𝑛 𝑧𝑎 ⋅𝜎 (√𝑛)(𝐸) = ( (√𝑛)(𝐸) = 𝐸 2 Multiply both sides of the equation by √𝑛. Multiplication property of equality. Divide both sides of the equation by E. Division property of equality. )(√𝑛) √𝑛 𝑧𝑎 ⋅ 𝜎 2 𝐸 9 Square both sides. 2 𝑧𝑎 ⁄2 ⋅ 𝜎 (√𝑛) = ( ) 𝐸 2 𝑛=( This is now the resulting formula for sample size needed in estimating a population mean. 𝑧𝑎⁄ ⋅𝜎 2 2 ) 𝐸 Formula in Determining the Minimum Sample Size Needed when Estimating the Population Mean 𝑛=( 2 𝑧𝑎 ⁄2 ⋅ 𝜎 ) 𝐸 Where: 𝒛𝒂⁄ – is the z value 𝟐 𝝈 – standard deviation 𝒏 – number of sample E – margin of error Since the value of is usually unknown, it can be estimated by the standard deviation ( ) from a prior sample. Alternatively, we may approximate the range R of observations in the population and make a conservative estimate of ≈ R 4 . In any case, round up the value of obtained to ensure the sample size will be sufficient to achieve the specified reliability. Example 1: Feeding Program In a certain barangay, Mario wants to estimate the mean weight µ, in kilograms, of all seven-year-old children to be included in a feeding program. He wants to be 99% confident that the estimate of µ is accurate 0.06 kg. Suppose from a previous study, the standard deviation of the weights of the target population was 0.5kg, what should the sample size be? Note: The phrase “accurate to within 0.06 kg” indicates a narrowed width of the confidence interval. Thus, the decide error E= 0.06 kg. Population standard deviation = 0.5 kg. 10 Solution: Steps 1. Determine the given. 2. Determine the confidence coefficient Solution 99% confidence, E = 0.06 kg, a = 100% - 99% To determine the value of a, we can simply subtract the confidence level from 100%. a = 1 - .99 a = .01 𝑎/2 = 0.01/2 𝒂/𝟐 = 0.005 0.500 - 0.005 = 0.495 𝒛𝒂⁄ = 1.96 𝟐 3. Substitute the values in the formula and compute. = 0.5 kg Division property of equality. Subtract 0.005 from 0.500. Hence, Using the Area under the Standard Normal Curve Table. 2 𝑧𝑎 ⁄2 ⋅ 𝜎 𝑛=( ) 𝐸 (2.58)(0.5) 2 𝑛=( ) 0.06 2 𝑧𝑎 ⁄2 ⋅ 𝜎 𝑛=( ) 𝐸 1.29 2 𝑛=( ) 0.06 𝑛 = (21.5)2 𝒏 = 𝟒𝟔𝟐. 𝟐𝟓 or 463 4. Round up the resulting value to the nearest Thus, Mario needs a sample size of 463 . whole number. Note: When Determining sample size, we always round up the resulting value to the next whole number. Rule: When the calculated sample size is not a whole number, it should be rounded up to the next higher whole number. Rule: Rounding up a sample size calculation for conservativeness ensures that your sample size will always be the representative of the population. Reference: https://www.isixsigma.com/tools-templates/sampling-data/rounding-and-round-rules 11 Example 1. A sample size calculation determined that 2006.083 data points were necessary to represent the population. In this case, 2007 data points samples should be taken. 2. Suppose the calculated sample size is 409.14. What would be the sample size? 409.14? ____________ Answer: 410 Try this: D. Round up the following calculated sample size. 1. n = 207.39 2. n = 347.56 3. n = 976.09 Example 2. Replicating a study Kristine wants to replicate a certain study, where the lowest observed value is 10.4 while the highest is 12.8. She wants to estimate the population mean µ to within an error of 0.05 of its true value. Using 98% confidence level find the sample size n that she needs. Solution: Steps 1. Determine the given. 2. Determine the confidence coefficient. Solution 98% confidence, E = 0.06 kg, lowest observed value is 10.4 while the highest is 12.8. a = 100% - 98% a = 1 - .98 a = .02 𝑎/2 = 0.02/2 𝒂/𝟐 = 0.01 0.50 - 0.01 = 0.49 𝒛𝒂⁄ = 2.33 𝟐 12 To determine the value of a, we can simply subtract the confidence level from 100%. Division property of equality. Subtract 0.005 from 0.500. Hence, Using the Area under the Standard Normal Curve Table, 3. Determine the standard deviation. Since the range R = 12.8 – 10.4 = 2.4 Then, using the formula = 𝑅/4 = 2.4/4 = .6 4. Substitute the values in the formula and compute. 𝒛𝒂 ⁄ ⋅𝝈 𝒏=( 𝟐 ) 𝑬 𝑛= 𝑧𝑎⁄ ⋅𝜎 2 ( 2 ) 𝐸 𝑛=( 𝟐 𝑛=( (2.33)(0.6) ) 0.06 2 1.398 2 ) 0.06 𝑛 = (23.3)2 5. Round up the resulting value to the nearest whole number. 𝒏 = 𝟓𝟒𝟐. 𝟖𝟗 or 543 Thus, Kristine needs a sample size of 543. E. Solve this. 1. The school nurse of a certain school wants to conduct a survey about the average number of students who buy snacks at the school canteen. If he plans to use 98% confidence level, 3 as the margin of error, and a standard deviation of 15. How many sample sizes does he need for the survey? What’s More Activity 2 A. Round up the following calculated sample size. 1. n = 507.49 2. n = 247.51 3. n = 1, 276.08 13 4. n = 644.o41 5. n = 932.63 B. Find the length of the following confidence interval. 1. 0.241 < p < 0.653 2. 0.355 < p < 0.570 3. 0.475 < p < 0.735 4. Upper confidence limit = 0.996 Lower confidence limit = 0.436 5. Upper confidence limit = 0.886 Lower confidence limit = 0.245 C. Find the length of the confidence interval given the following data:(s – sample standard deviation) 1. 𝑠 = 2.36, n = 350, confidence level: 99% 2. 𝑠 = 3.35, n = 250, confidence level: 99% 3. 𝑠 = 3, n = 275, confidence level: 95% 4. 𝑠 = 6, n = 425, confidence level: 98% 5. 𝑠 = 9, n = 501, confidence level: 99% D. Determine the sample size, given the following data: (s – sample standard deviation) 1. 𝑠 = 5, E = 2.45, confidence level: 95% 2. 𝑠 = 7, E = 3.65, confidence level: 98% 3. 𝑠 = 4, E = 2.76, confidence level: 99% 4. 𝑠 = 8, E = 2.22, confidence level: 95% 5. 𝑠 = 3.3, E = 1.03, confidence level: 99% What I Have Learned I. Fill in the blanks. Write your answer on your answer sheet. A confidence interval, in statistics, refers to the probability that a _____(1)_______ parameter will fall between a set of values for a certain proportion of times. Confidence intervals measure the degree of uncertainty or certainty in 14 a ______(2)______ method. They can take any number of probability limits, with the most common being a 95% or 99% confidence level. _____(3)______ is the absolute difference between the upper confidence limit and the lower confidence limit. There are two things to remember when we decided on the quality of the sample size we need: ____(4)______ and the _____(5)_____ of the interval. What I Can Do Solve the following problems. Write your answer on your answer sheet. 1. You want to estimate the mean gasoline price within your town to the margin of error of 5 centavos. Local newspaper reports the standard deviation for gas price in the area is 25 centavos. What sample size is needed to estimate the mean gas prices at 95% confidence level? 2. Carlos wants to replicate a study where the highest lowest observed value is 13.8 while the lowest is 13.4. He wants to estimate the population mean µ to the margin of error of 0.025 of its true value. Using 99% confidence level, find the sample size n that he needs. Assessment A. Find the length of the following confidence interval. 1. 0.242 < p < 0.653 2. 0.345 < p < 0.570 3. 0.275 < p < 0.463 15 4. Upper confidence limit = 0.820 Lower confidence limit = 0.490 5. Upper confidence limit = 0.715 Lower confidence limit = 0.350 B. Find the length of the confidence interval given the following data: 6. s = 5.36, n = 350, confidence level: 99% 7. s = 2.35, n = 250, confidence level: 99% 8. s = 1.20, n = 200, confidence level: 95% 9. s = 8.15, n = 29, confidence interval: 99% 10. s = 3.25, n = 17, confidence interval: 95% C. Solve the following problems. 11. In a group presentation, the average geometric reasoning of Grade 10 students in a Mathematics camp was observed to be 80 with s standard deviation of 4. A researcher wants to replicate the study to estimate the true population mean µ to within 0.5 maximum error. If the 98% level of confidence is adopted, how many respondents are needed? 12. Teacher Carol, wants to conduct a survey about the average number of students in a certain school who wants online class instead of distance modular learning. If she plans to use 99% confidence level, 0.5 as the margin of error, and a standard deviation of 5. How many sample sizes does she need for the survey? 16 Additional Activities A. Determine the sample size, given the following data: 1. 𝑠 = 6, E = 0.5, confidence level= 95% 2. 𝑠 = 5, E =0.04, confidence level=98% 3. 𝑠 = 8, E = 3, confidence level=99% 4. 𝑠 = 10, E = 5, confidence level=95% 5. 𝑠 = 7, E = 2, confidence level= 99% B. Solve the following problems. 1. A researcher wants to estimate the average number of children with congenital heart disease who are between the ages of 1–5 years old. How many children should be enrolled in this study, if the researcher plans on using a 95% confidence level and wants a margin of error of 0.5 and standard deviation 4? 2. Allan, a Grade 12 senior high school student, wants to estimate the average number of students who will pursue collage degree in a certain school. How many sample sizes does he need, if he plans to use 98% confidence, 0.5 as the margin of error, and a standard deviation of 5. C. Find other methods of determining sample size, then compare these with the formula proposed in this module. If you are to select a method, which will it be? Explain your idea. 17 What I Have Learn 1. Population 2. Sampling 3. Length of confidence interval 4. confidence 5. narrowness What I Can Do 1. n = 97 2. n = 107 What’s New A. 1. 0.115 2. 0.36 3. 0.26 4. 0.37 5. 0.331 18 Additional Activities A. 1. 554 2. 849 3. 48 4. 16 5. 82 B. 1. 246 2. 543 C. Students’ answers may vary. Assessment 1. 0.411 2. 0.215 3. 0.178 4. 0.33 5. 0.365 6.1.4783 7. 0.7669 8. 0.3326 9. 8.3631 10. 3.2327 11. n = 543 12. n = 666 What I Know 1. 0.5345 2. 0.27 3. 0.302 4. 0.157 5. 0.271 6. 1.9169 7. 2.0004 8. 1.2025 9. 5.5939 10. 9.1483 What’s In A.1. 112 2. percentage 3. 1.96 4. 0.01 5. standard error 6. Sample size B. 1. 0.62 2. 0.2275 3. 65.33 4. 2,615.81 5. 4,160.25 What Is It B. 1. 0.2084 2. 0.2771 3. 0.9251 C. 1. 5.1096 2. 2.8896 3. 2.6183 D. 1. 208 2. 348 3. 977 E. 1. 136 What’s More Activity 2 A. C. 1.508 2.248 3.1,277 4.645 5. 933 B. D. 1. 0.412 2. 0.215 3. 0.26 4. 0.56 5. 0.641 1. 0.6509 2. 1.0933 3. 0.7092 4. 1.5018 5. 2.0748 1. 16 2. 20 3. 14 4. 50 5. 69 Answer Key References Books Alonzo, George A. (2017). Statistics and Probability For Senior High School, Salinlahi Publishing House, Inc., 1206 Cardonia St. Barangay Poblacion, Makati City, Philippines. Belecina, Rene R. et. al. (2016). Statistics and Probability. 1st ed. Rex Bookstore, 856 Nicanor Reyes Sr. St. Sampaloc, Manila. Websites Cole, Neal. “Z Score – definition and How to Use – Conversion Uplift”. https://www.google.com/search?q=z+values+table&tbm=isch&ved=2ahUKE wiZkOnikrfuAhUbI6YKHSBlDBEQ2-cCegQIABAA&oq=z+values&gs_lcp=CgN pbWcQARgAMgQIABBDMgQIABBDMgQIABBDMgQIABBDMgQIABBDMgIIAD ICCAAyAggAMgIIADoGCAAQBxAeOggIABAIEAcQHjoKCAAQsQMQgwEQQ1D 8oxBY6v8QYOCREWgAcAB4AIABgwGIAfYEkgEDNy4xmAEAoAEBqgELZ3dzL Xdpei1pbWfAAQE&sclient=img&ei=x8EOYNmQLpvGmAWgyrGIAQ&bih=912 &biw=1920&rlz=1C1CHBD_enPH913PH913#imgrc=F0JP0o8NizNdrM Confidence Intervals. https://handbook-51.cochrane.org/chapter_12/12_4_1_confidence_intervals.htm iSixSigma-Editorial. “Sample Size Round-off”. https://www.isixsigma.com/toolstemplates/sampling-data/rounding-and-round-rules Mathematics Stack Exchange. “Calculate Critical Value”. https://www.google.com/search?q=t+table+critical+values&rlz=1C1CHBD_e nPH913PH913&sxsrf=ALeKk00PCvAoqB3o1ENz-ywgil0pIj0PyQ:1611579845 695&tbm=isch&source=iu&ictx=1&fir=Ak3E8SGWtJZSvM%252C3IfNW_1KN -XacM%252C_&vet=1&usg=AI4_-kQMLXnmB3gxGk_tBC4xSwP6EoE1oA 19 For inquiries or feedback, please write or call: Department of Education – Region III, Schools Division of Bataan - Curriculum Implementation Division Learning Resources Management and Development Section (LRMDS) Provincial Capitol Compound, Balanga City, Bataan Telefax: (047) 237-2102 Email Address: bataan@deped.gov.ph