251y0612 2/17/06 ECO251 QBA1 FIRST EXAM February 16 and 17, 2006 ECO251 QBA1 Name: _____Key_____________ Student Number : _____________________ Class Hour: _____________________ Remember – Neatness, or at least legibility, counts. In most non-multiple-choice questions an answer needs a calculation or short explanation to count. Part I. (7 points) (Source: Harvey J. Brightman) The following numbers are a sample and represent the pulse rates of 10 well-conditioned athletes. 31, 33, 36, 36, 37, 47, 44, 41, 39, 39. Compute the following: Show your work! a) The Median (1) b) The Standard Deviation (3) c) The 46th percentile (2) d) The Coefficient of variation (1) Solution: Index x x2 1 31 961 2 33 1089 3 36 1296 4 36 1296 5 37 1369 6 47 2209 7 44 1936 8 41 1681 9 39 1521 10 39 1521 Total 383 14879 x in order 31 33 36 36 37 39 39 41 44 47 n 10 a) Median: position pn 1 .511 5.5 a.b The middle numbers are the 5th and 6th number, which x5 x6 38 . 2 x5 .5( x6 x5 ) 37 .539 37 37 1 38 are 37 and 39. The median is the average of two middle numbers. x.50 Or x1 p xa .b( xa1 xa ) . So x.50 x 383 38.3 , s x b) Standard Deviation: x 2 2 nx 2 14879 10 38 .32 10 1 n 10 n 1 210 .1 23 .3444 . So s 23.3444 4.8316 . Note that saying a standard deviation is zero is equivalent 9 to saying that all values of x are the same. c) 46th percentile: position pn 1 .4611 5.06 . So a 5 and .b 0.06 x1 p xa .b( xa1 xa ) and x1.46 x.54 x5 0.06( x6 x5 ) 37 0.06 (39 37 ) 37 .12 d) C s 4.8316 0.1262 or 12.63% x 38 .3 1 251y0612 2/17/06 How this was done on Minitab – Version 2 Data x was placed in c1 (column 1). MTB > describe c1 Descriptive Statistics: C1 Variable C1 N 10 N* 0 Mean 38.30 SE Mean 1.53 StDev 4.83 Minimum 31.00 MTB > let c3 = c1*c1 MTB > Sort c1 c5; Compute x 2 in column 3. SUBC> By c1. MTB > sum c1 x in order is put in column 5. Q1 35.25 Median 38.00 Q3 41.75 Maximum 47.00 Sum of C1 Sum of C1 = 383 MTB > sum c3 Sum of C3 Sum of C3 = 14879 MTB > print c1 c3 c5 Data Display Row 1 2 3 4 5 6 7 8 9 10 C1 31 33 36 36 37 47 44 41 39 39 C3 961 1089 1296 1296 1369 2209 1936 1681 1521 1521 C5 31 33 36 36 37 39 39 41 44 47 2 251y0612 2/17/06 Part II. (At least 35 points – 2 points each unless marked - Parentheses give points on individual questions. Brackets give cumulative point total.) Exam is normed on 50 points. 1. (Brightman) At an urban university, there are 200 undergraduates whose ages are between 16 and 17, 7000 undergraduates whose ages are between 18 and 23, 2000 undergraduates between 24 and 29 years old, 1000 undergraduates between 30 and 35 years old and 1000 who are older than 35. a) Without doing any math, explain in plain English whether the mean will be below, the same as or above the median and why. (2) Answer: The 1000 people above 35 will pull the mean way up above the median. This distribution is skewed to the right. b) Where will the mode be relative to the mean and median? (1) [3] Answer: Since the median is usually between the mean and the mode, the mode must lie to the left of the mean and mode. If you made a diagram, it would show, left to right, mean median mode. 2. I have the average time of 10 randomly picked runners in the Boston Marathon. a) Is this a parameter or a statistic? Answer: This describes a sample and must be a statistic. A parameter describes a population. b) What symbol should you use to indicate this mean? Answer: The symbol for a sample mean is x . [5] 3. For a rather shapeless distribution with one mode, a mean of 100 and a standard deviation of 4, we can say that the percent of data falling between 80 and 120 is a) *At least 96% b) At most 96% c) 100% d) At least 99% e) At most 99% f) None of the above. [7] Explanation: 120 is 100 + 5(4). 80 is 100 - 5(4). The Tchebyschev inequality says that the fraction of measurements more than k 5 standard deviations from the mean is, at most, 1 24 1 1 1 25 . So the fraction between 80 and 120 is at least 1 25 25 96 % . k2 52 4. For a mound-shaped (symmetrical) distribution with one mode, a mean of 100 and a standard deviation of 2, we can say that the percent of data falling above 96 is a) About 95% b) *About 97.5% c) About 68% d) Almost 100% e) None of the above Explanation: 96 is 100 - 2(2), i.e. 2 standard deviations below 100. The Empirical Rule says that 95% of data points will fall within 2 standard deviations of the mean. 5% will be in the tails of the distribution, because of symmetry, half (2.5%) will be above 100 + 2(2) = 104. The total is thus 95% + 2.5% = 97.5%. 5. The drawing of inferences about an unknown part from a known whole is a) *Deductive reasoning b) Inductive reasoning c) Census taking d) Sampling e) None of the above. [11] 3 251y0612 2/17/06 6. Observations about a continuous quantitative variable a) Can be made in only two categories b) Can assume values only at specific points of a scale of values with inevitable gaps between these points. c) *Can assume values at all points of a scale of values with no breaks in between possible values. d) Cannot be meaningfully multiplied or divided. e) Both b) and d) are true. [13] 7. Mark the variables below as qualitative or categorical (A), quantitative and continuous (B1) or quantitative and discrete (B2) (1 each) a) Number of shoes sold B2 b) Total sales of shoes in dollars and cents B1 c) A list numbering the best-selling shoe models from 1 to 10 A d) Reorder numbers (codes ) of shoe models A [17] Explanation: The list numbering the best-selling shoe models from 1 to 10 is ordinal data, which is a form of qualitative data. 8. If I double all of the incomes in a sample of 1000 people, mark below which of the statistics will change. a) The standard deviation b) The coefficient of variation. c) Relative skewness 1 or g1 d) All of the above will change e) None of the above will change . [19] Explanation: Only the standard deviation will change. Relative skewness and the coefficient of variation are both dimension-free quantities, so both the numerator and denominator will double. 4 251y0612 2/17/06 TABLE 2-13 Given below is the stem-and-leaf display representing the amount of detergent used in gallons (with leaves in 10ths of gallons) in a month by 25 drive-through car wash operations in Phoenix. (Ng p57) 9 | 047 10 | 02238 11 | 135556777 12 | 22348 13 | 008 Note Correction!!!!! 9. In table 2-13, if a percentage histogram is constructed using 9.0 through 9.9 as the first class, what percent will be in the 12-12.9 class? [21] Solution: 20%. The frequency table would read Class f rel f 3 3 5 5 11-11.9 9 9 12-12.9 5 13-13.9 3 9- 9.9 10-10.9 Sum n 25 25 12 % 25 20 % 25 36 % 5 20 % 25 3 12 % 25 10. In table 12.3 find the median amount of detergent used. position pn 1 .526 13.0 a.b . The 13th number is 11.5. [23] 11. Using the data in table 12.3. Assume that the data is to be presented in 7 classes, show how you would decide what class interval to use and list the classes below with their frequencies. (5) [28] 13 .9 9.0 0.6833 . If you Solution: The numbers go from 9.0 to 13.9. The calculation is thus 7 use 1, your last class will be empty, so try .7 or .75. or .8. 9 | 047 10 | 02238 11 | 135556777 12 | 22348 13 | 008 A B C D E F G 9.0 9.7 10.4 11.1 11.8 12.5 13.2 Class to under to under to under to under to under to under to under 9.7 10.4 11.1 11.8 12.5 13.2 13.9 Frequency 2_ 5_ 1_ 9_ 4_ 3_ 1_ 5 251y0612 2/17/06 12. In Problem 3.42 in the text, data on waiting times in a bank in a commercial district is given. Assume that the 5-number summary is {0.38, 3.24, 4.50, 5.53, 10.03}. Use this to make a horizontal box plot, but first find the interquartile range. Then do the following: An upper fence is defined as Q3 + 1.5(IQR) and a lower fence is Q1 – 1.5(IQR). Indicate the fences by vertical lines at the end of the whiskers in your box plot – do not let the whiskers extend beyond the fences, but only show a fence if there is data beyond it. Any points beyond the fence should be represented by dots. (4) [32] Drawing: IQR = 5.53 - 3.24 = 2.19. 1.5(IQR) = 3.285. Lower fence is 3.24 – 3.285 = -0.045 . Upper fence is 5.53 + 3.285 = 8.815. Whiskers go from 0.38 to 3.24 and 5.53 to 8.815. Box goes from 3.24 to 5.53. Median stripe is at 4.50. Using the word drawing tool, this is the closest I could come. 0 1 2 3 4 5 6 7 8 9 10 11 13. What characteristic do the variance, interquartile range and the coefficient of variation have that they do not share with the mean and Pearson’s measurement of skewness? (1) [33] Answer: They are measures of dispersion. 14. The following data represents proven oil deposits in billions of barrels divided by region. Show this as a Pareto chart. (5) [37] Billions of Per Cent of Barrels Total North America 54.8 5.2 Central and South America Western Europe Africa Middle East Far East and Oceania Eastern Europe and CIS 95.2 17.2 74.9 683.6 63.0 59.0 9.1 1.6 7.2 65.3 6.0 5.6 Drawing: Your graph should be a bar graph with a line above the bars with the following points marked: Region Middle C and S Africa F East & E Europe N America W. Europe East America Oceania and CIS Location 65.3% 74.7% 81.6% 87.6% 93.2% 98.4% 100% of line Height of 65.3% 9.1% 7.2% 6.0% 5.6% 5.2% 1.6% Bar 6 251y0612 2/17/06 ECO251 QBA1 FIRST EXAM February 16 and 17, 2006 TAKE HOME SECTION Name: _________________________ Student Number: _________________________ Throughout this exam show your work! Please indicate clearly what sections of the problem you are answering and what formulas you are using. Turn this is with your in-class exam. Part IV. Do all the Following (12+ Points). These are based on problems by Edward J. Kane. Show your work! 1. The following numbers give us the frequency distributions of interest rate changes in the US between 1801 and 1961 (153 years). Treat these data as a sample. Personalize the data below by adding the last digit of your student number to the first frequency and the second to last digit of your student number to the second frequency. For example, Seymour Butz’s student number is 876509 so he adds 9 to first frequency and 0 to the second frequency and uses {10, 2, 9, 25, 65, 35, 10, 5, and 1} (over 162 years). You may check your work on the computer, but what is turned in should look as if it had all been done by hand. Class Frequency a. Calculate the Cumulative Frequency (0.5) b. Calculate the Mean (0.5) -.95 to -.76 1 c. Calculate the Median (1) -.75 to -.56 2 d. Calculate the Mode (0.5) -.55 to -.36 9 e. Calculate the Variance (1.5) -.35 to -.16 25 f. Calculate the Standard Deviation (1) -.15 to .04 65 g. Calculate the Interquartile Range (1.5) .05 to .24 35 h. Calculate a Statistic showing Skewness and .25 to .44 10 .45 to .64 5 interpret it (1.5) .65 to .84 1 i. Make an ogive of the data (Neatness Counts!)(1) j. Extra credit: Put a (horizontal) box plot below the ogive chart using the same horizontal scale (1) Solution using the original numbers: If we use the original numbers and the computational method, we get the following for the frequencies. Frel Row Class f f rel F 1 -.95 to -.76 1 2 -.75 to -.56 2 3 -.55 to -.36 9 4 -.35 to -.16 25 5 -.15 to .04 65 6 .05 to .24 35 7 .25 to .44 10 8 .45 to .64 5 9 .65 to .84 1 Total 153 0.006536 0.013072 0.058824 0.163399 0.424837 0.228758 0.065359 0.032680 0.006536 1.00000 1 3 12 37 102 137 147 152 153 0.00654 0.01961 0.07843 0.24183 0.66667 0.89542 0.96078 0.99346 1.00000 7 251y0612 2/15/06 If we use the computational method we get the following table. x Row Class f fx fx2 fx3 1 -.95 to -.76 1 2 -.75 to -.56 2 3 -.55 to -.36 9 4 -.35 to -.16 25 5 -.15 to .04 65 6 .05 to .24 35 7 .25 to .44 10 8 .45 to .64 5 9 .65 to .84 1 Total 153 -0.85 -0.65 -0.45 -0.25 -0.05 0.15 0.35 0.55 0.75 -0.85 -1.30 -4.05 -6.25 -3.25 5.25 3.50 2.75 0.75 -3.45 0.7225 0.8450 1.8225 1.5625 0.1625 0.7875 1.2250 1.5125 0.5625 9.2025 -0.614125 -0.549250 -0.820125 -0.390625 -0.008125 0.118125 0.428750 0.831875 0.421875 -0.581625 If we like to work, we may have used the definitional method instead. Row Class f 1 -.95 to -.76 1 2 -.75 to -.56 2 3 -.55 to -.36 9 4 -.35 to -.16 25 5 -.15 to .04 65 6 .05 to .24 35 7 .25 to .44 10 8 .45 to .64 5 9 .65 to .84 1 Total 153 x -0.85 -0.65 -0.45 -0.25 -0.05 0.15 0.35 0.55 0.75 xx f x x -0.85 -1.30 -4.05 -6.25 -3.25 5.25 3.50 2.75 0.75 -3.45 -0.827451 -0.627451 -0.427451 -0.227451 -0.027451 0.172549 0.372549 0.572549 0.772549 -0.82745 -1.25490 -3.84706 -5.68627 -1.78431 6.03922 3.72549 2.86275 0.77255 0.00000 From the f and fx columns of either display, we find n mean is x n 0.68468 0.78739 1.64443 1.29335 0.04898 1.04206 1.38793 1.63906 0.59683 9.12471 f 153 fx 3.45 0.022549 . We also find that 153 f x x 3 f x x 2 fx fx 2 -0.566535 -0.494048 -0.702913 -0.294173 -0.001345 0.179807 0.517071 0.938443 0.461082 0.037389 and fx 9.2025 , 3.45 , so that the fx 3 0.581625 , f x x 0 (except for a rounding error), f x x 2 9.12471, and f x x 3 0.0373887. The width of all these intervals is 0.75 0.95 0.20 . (Note that, to be reasonable, the mean, median and quartiles must fall between -0.95 and 0.85.) a. Calculate the Cumulative Frequency (0.5): See the F column on the previous page. fx 3.45 b. Calculate the Mean (0.5): We have already found x 0.022549 . n 153 c. Calculate the Median (1): position pn 1 .5153 76.5 . This is above F 37 and below pN F w so f p F 102 , so the interval is the 5th, -0.15 to 0.04, which has a frequency of 65. x1 p L p .5153 37 x1.5 x.5 0.15 0.20 0.15 0.6077 0.20 0.028462 65 d. Calculate the Mode (0.5): The mode is the midpoint of the largest group. Since 65 is the largest frequency, the modal group is -0.15 to 0.04 and the mode is -0.05. Note that to be reasonable, Q1 x50 Q3 and that Q1, x50 , Q3, x and the mode must be between -0.95 and 0.85! fx 2 nx 2 9.20250 153 0.022549 2 9.12471 2 e. Calculate the Variance (1.5): s 0.060031 n 1 152 152 or s 2 f x x n 1 2 9.12471 0.060031 . The computer got 0.066310. 152 f. Calculate the Standard Deviation (1): s 0.060031 0.245012 8 251y0612 2/15/06 g. Calculate the Interquartile Range (1.5): First Quartile: position pn 1 .25154 38.5 . This is above F 37 and below F 102 , so the interval is the 5th, -0.15 to 0.04, which has a frequency of 65. pN F .25153 37 x1 p L p w gives us Q1 x1.25 x.75 0.15 0.20 65 f p 0.15 0.019231 0.20 0.146154 . Third Quartile: position pn 1 .75154 115 .50 . This is above F 102 and below F 137 , so the interval is the 6th, 0.05 to 0.24 which has a frequency of 35. .75153 102 x1.75 x.25 0.05 0.20 0.05 0.364286 0.20 0.122857 .. 35 IQR Q3 Q1 0.122857 0.146154 0.269011 . h. Calculate a Statistic showing Skewness and interpret it (1.5): We had n 153 and that the mean is x 0.022549 . We also found that f x x 3 k 3 fx 2 9.2025 , fx 3 fx 3.45 , so 0.581625 and 0.037389. x.5 0.028462 and mo 0.05. n (n 1)( n 2) fx 3 3x fx 2 2nx 3 153 0.581625 3 0.022549 9.2025 2153 0.022549 3 152 151 0.00666609 0.581625 0.622522 0.003508 0.00666609 .037389 0.000249 . or k 3 n (n 1)( n 2) or g 1 k3 or s 3 f x x 0.000249236 0.245012 3 3 153 0.037389 0.0002492 152 151 The computer gets 0.000249236 0.0169453 Pearson's Measure of Skewness SK Actually, this should be SK1 3mean mode 3 0.022549 0.05 .3361 std .deviation 0.245012 mean mode 0.022549 0.05 .1120 or std .deviation 0.245012 3mean median 3 0.022549 0.028462 .0724 0.245012 std .deviation Because of the positive sign, the measures all imply skewness to the right.. SK 2 i. Make an ogive of the data (Neatness Counts!)(1): An ogive is a simple line graph with cumulative frequency on the y-axis and the numbers -0.95 to 0.84 (actually 0 to 1 would be fine) on the x-axis. Each F or Frel point is plotted against the upper limit of the class, x . In addition 1 empty class must be added at the beginning. The first point on your graph should be (-0.95, 0); the next point is (-0.75, 3) or (-.75, .00654). At x 0.85 the height of the line should be either 153 or 1. After this point the ogive is a horizontal line. j. Extra credit: Put a (horizontal) box plot below the ogive chart using the same horizontal scale (1) The five-number summary is [-0.95 (or -0.85), -0.146154 , -0.28462, 0.122857, 0.85(or .75)] IQR Q3 Q1 0.122857 0.146154 0.269011 . 1.5IQR 0.403516 . If you use fences, they should be at 0.146154 .403516 0.5577 and 0.122857 .403516 0.52537 . So the box extends from (-.146154) to .122857, with a median marked by a horizontal line at -0.028462. The whiskers go from the box to -.5577 and 0.52537 with dotted lines showing the full range. 9 251y0612 2/15/06 Solution using the original numbers with nines added to the first two frequencies: If we use these new numbers and the computational method, we get the following for the frequencies. Frel Row Class f f rel F 1 -.95 to -.76 10 2 -.75 to -.56 11 3 -.55 to -.36 9 4 -.35 to -.16 25 5 -.15 to .04 65 6 .05 to .24 35 7 .25 to .44 10 8 .45 to .64 5 9 .65 to .84 1 Total 171 0.058480 0.064327 0.052632 0.146199 0.380117 0.204678 0.058480 0.029240 0.005848 1.00000 10 21 30 55 120 155 165 170 171 0.05848 0.12281 0.17544 0.32164 0.70175 0.90643 0.96491 0.99415 1.00000 If we use the computational method we get the following table. x Row Class f fx fx2 fx3 1 -.95 to -.76 10 2 -.75 to -.56 11 3 -.55 to -.36 9 4 -.35 to -.16 25 5 -.15 to .04 65 6 .05 to .24 35 7 .25 to .44 10 8 .45 to .64 5 9 .65 to .84 1 Total 171 -0.85 -0.65 -0.45 -0.25 -0.05 0.15 0.35 0.55 0.75 -8.50 7.2250 -7.15 4.6475 -4.05 1.8225 -6.25 1.5625 -3.25 0.1625 5.25 0.7875 3.50 1.2250 2.75 1.5125 0.75 0.5625 -16.95 19.5075 -6.14125 -3.02088 -0.82013 -0.39063 -0.00813 0.11813 0.42875 0.83188 0.42188 -8.58138 If we like to work, we may have used the definitional method instead. Row Class f 1 -.95 to -.76 10 2 -.75 to -.56 11 3 -.55 to -.36 9 4 -.35 to -.16 25 5 -.15 to .04 65 6 .05 to .24 35 7 .25 to .44 10 8 .45 to .64 5 9 .65 to .84 1 Total 171 x -0.85 -0.65 -0.45 -0.25 -0.05 0.15 0.35 0.55 0.75 fx -8.50 -7.15 -4.05 -6.25 -3.25 5.25 3.50 2.75 0.75 -16.95 xx -0.750877 -0.550877 -0.350877 -0.150877 0.049123 0.249123 0.449123 0.649123 0.849123 f x x -7.50877 5.63817 -6.05965 3.33812 -3.15789 1.10803 -3.77193 0.56910 3.19298 0.15685 8.71930 2.17218 4.49123 2.01711 3.24561 2.10680 0.84912 0.72101 0.00000 17.8274 From the f and fx columns of either display, we find n mean is x 171 f x x 3 -4.23357 -1.83890 -0.38878 -0.08586 0.00770 0.54114 0.90593 1.36757 0.61223 -3.11254 f 171 and fx fx 16.95 0.0991228 . We also find that n f x x 2 fx 2 19 .5075 , 16 .95 , so that the fx 3 3.11254 , f x x 0 (except for a rounding error), f x x 2 17.8274, and f x x 3 3.11254 . The width of all these intervals is 0.75 0.95 0.20 . (Note that, to be reasonable, the mean, median and quartiles must fall between -0.95 and 0.85.) a. Calculate the Cumulative Frequency (0.5): See the F column above. fx 16 .95 b. Calculate the Mean (0.5): We have already found x 0.0991228 . n 171 c. Calculate the Median (1): position pn 1 .5172 86 . This is above F 55 and below F 120 , pN F so the interval is the 5th, -0.15 to 0.04, which has a frequency of 65. x1 p L p w so f p .5171 55 x1.5 x.5 0.15 0.20 0.15 0.4692 0.20 0.0561539 65 d. Calculate the Mode (0.5): The mode is the midpoint of the largest group. Since 65 is the largest frequency, the modal group is -0.15 to 0.04 and the mode is -0.05. 10 251y0612 2/15/06 e. Calculate the Variance (1.5): s 2 or s 2 f x x n 1 2 fx 2 nx 2 n 1 19 .5075 171 0.0991228 170 2 17 .82737 0.104867 170 17 .8274 0.104867 . The computer got 0.104867. 170 f. Calculate the Standard Deviation (1): s 0.104867 0.323832 g. Calculate the Interquartile Range (1.5): First Quartile: position pn 1 .25172 43 . This is above F 30 and below F 55, so the interval is the 4th, -0.35 to 0.16, which has a frequency of 25. pN F .25171 30 x1 p L p w gives us Q1 x1.25 x.75 0.35 0.20 25 f p 0.35 0.5100 0.20 0.248000 . Third Quartile: position pn 1 .75172 129 . This is above F 120 and below F 155 , so the interval is the 6th, 0.05 to 0.24 which has a frequency of 35. .75 171 120 x1.75 x.25 0.05 0.20 0.05 0.23571 0.20 0.097143 .. 35 IQR Q3 Q1 0.097143 0.248000 0.345143 . h. Calculate a Statistic showing Skewness and interpret it (1.5): We had n 171 and so that the mean is x 0.0991228 . We also found that f x x 3 k 3 fx 2 19 .5075 , fx 3 fx 16 .9500 , 8.58038 and 3.11254 . x.5 0.0561539 and mo 0.05. n (n 1)( n 2) fx 3 3x fx 2 2nx 3 171 8.58038 3 0.0991228 19 .5075 2171 0.0991228 3 170 169 0.00595197 8.58038 5.800914 0.333079 0.00595197 3.112545 0.018526 . n 171 3.11254 0.00595197 3.11254 0.018526 . f x x 3 (n 1)( n 2) 170 169 The computer gets -0.0185257 k 0.018526 0.5455 or g 1 33 s 0.323832 3 or k 3 or Pearson's Measure of Skewness SK Actually, this should be SK1 3mean mode 3 0.0991228 0.05 0.4551 std .deviation 0.323832 mean mode 0.0991228 0.05 0.1517 or std .deviation 0.323832 3mean median 3 0.0991228 0.0561539 .5547 SK 2 0.2323832 std .deviation Because of the negative sign, the measures all imply skewness to the left. i. Make an ogive of the data (Neatness Counts!)(1): An ogive is a simple line graph with cumulative frequency on the y-axis and the numbers -0.95 to 0.84 (actually 0 to 1 would be fine) on the x-axis. Each F or Frel point is plotted against the upper limit of the class, x . In addition 1 empty class must be added at the beginning. The first point on your graph should be (-0.95, 0); the next point is (-0.75, 10) or (-.75, 0.05848). At x 0.85 the height of the line should be either 171 or 1. After this point the ogive is a horizontal line. 11 251y0612 2/15/06 j. Extra credit: Put a (horizontal) box plot below the ogive chart using the same horizontal scale (1) The five-number summary is [-0.95 (or -0.85), -0.248000 , -0.0561539, 0.097143, 0.85(or .75)] IQR Q3 Q1 0.097143 0.248000 0.345143 . 1.5IQR 0.517715 . If you use fences, they should be at 0.248000 .517715 0.7657 and 0.097143 .517715 0.6149 . So the box extends from (-.0.248000) to .097143, with a median marked by a horizontal line at -0.0561539. The whiskers go from the box to -.7657 and 0.6149 with dotted lines showing the full range. 12 251y0612 2/15/06 2. The following problems (1 point each) are given in their raw form. Personalize them by using the third to last and second to last numbers in your student number. Add them as percents to the first two percents in a) and then add them to the first two numbers in b) and finally in c) divide them by 100 and add them to the first two numbers. For example, Seymour Butz’s student number is 876509, so he uses 5 and 0. This means in a) the percents are 5% + 5% =10%, 10% + 0% = 10%, -1%, 3%, and 6%, in b) the speeds are 55 + 5 = 60, 30 + 0 = 30, 70, 35 and 80 and in c) the numbers are 0.01 + 0.05 = 0.06, 0.25 + 0.00 = 0.25, 0.37, 0.26, 0.85 and 0.27 a) Geometric Mean Over 5 years GDP grew at 5%, 10%, -1%, 3% and 6%. Modify these as was done in the example given in class and use the geometric mean to find the average rate of growth. b) Harmonic mean I drive 300 miles a day, on the first day at (an average of) 55 mph, on the second at 30 mph, on the third at 70 mph, on the 4th at 35 mph and on the last at 80 mph. Use the harmonic mean to find my average speed over 2 days. c) Root-mean-square Find the rms of the following numbers: 0.01, 0.25, 0.37, 0.26, 0.85 and 0.27. If you wish, d) Compute the geometric mean from a) using natural and/or base 10 logarithms. (1 point extra credit each). Solution: Using the original data, before I started, I computed the following table. (1) (2) Row growth growth Natural logarithm mph 1/mph y y2 rates rates as plus decimals one 1 2 3 4 5 6 0.05 0.10 -0.01 0.03 0.06 1.05 1.10 0.99 1.03 1.06 logarithm of (2) 0.0487902 0.0953102 -0.0100503 0.0295588 0.0582689 0.221878 of (2) to base ten 0.0211893 0.0413927 -0.0043648 0.0128372 0.0253059 0.0963603 55 30 70 35 80 0.0181818 0.0333333 0.0142857 0.0285714 0.0125000 0.106872 0.01 0.25 0.37 0.26 0.85 0.27 0.0001 0.0625 0.1369 0.0676 0.7225 0.0729 1.0625 a) The Geometric Mean. For average growth rates add 1 to each rate. 1 x g x1 x 2 x3 x n n n x 5 1.05 1.10 0.99 1.031.06 5 1.24842 1.24842 1 5 1.24842 0.2 1.04537 So the average growth rate was 4.537%. b) The Harmonic Mean. 1 1 xh n 1 1 1 x 5 55 30 70 35 80 5 0.0181818 0.033333 0.014857 0.0285714 0.125000 1 1 1 1 0.106872 0.0213745 . 5 1 1 So xh 1 1 n 1 x 1 46 .7848 . 0.0213745 Of course some of you decided that 1 1 1 1 1 1 1 1 1 ? 1 xh n x 5 55 30 70 35 80 1 ??? . 5 55 30 70 35 80 This is, of course, an easier way to do the problem, and you will get an A for the course if you can 1 1 1 prove to me that ? . 2 2 4 13 251y0612 2/15/06 c) The Root-Mean-Square. 1 1 2 x rms x 2 0.01 2 0.25 2 0.37 2 0.26 2 0.85 2 0.27 2 n 6 1 1 0.0001 0.0625 0.1369 0.0676 0.7225 0.0729 1.0625 0.177983 6 6 So x rms 1 n x 2 0.17783 0.4208 . 2 1 1 1 x 2 ??? x 2.012 . This is, of course, an n n 12 easier way to do the problem, but I warned you that it wouldn’t work. It is equivalent to believing that 22 22 42 . 2 Of course some of you decided that x rms d) (i) Geometric mean using natural logarithms 1 ln( x) 1 ln 1.05 ln 1.10 ln 0.99 ln 1.03 ln 1.06 ln x g n 5 1 1 0.0487902 0.0953102 0.0100503 0.0295588 0.0582689 0.221878 0.0443755 5 5 x g e 0.0443755 1.04537 . So (ii) Geometric mean using logarithms to the base 10 1 log( x) 1 log 1.05 log 1.10 log0.99 log 1.03 log 1.06 log x g n 5 1 1 0.0211893 0.0413927 0.0043648 0.0.0128372 0.0.0253059 0.0963603 0.0192721 5 5 So x g 10 0.0192721 1.04537 Solution: Using the original data with nines added to the first two numbers, before I started, I computed the following table. (1) (2) Row growth growth Natural logarithm mph 1/mph y y2 1 2 3 4 5 6 rates as decimals 0.14 0.19 -0.01 0.03 0.06 rates logarithm of (2) plus of to base one (2) ten 1.14 0.131028 0.0569049 1.19 0.173953 0.0755470 0.99 -0.010050 -0.0043648 1.03 0.029559 0.0128372 1.06 0.058269 0.0253059 0.382759 0.166230 64 39 70 35 80 0.0156250 0.0256410 0.0142857 0.0285714 0.0125000 0.0966232 0.10 0.34 0.37 0.26 0.85 0.27 0.0100 0.1156 0.1369 0.0676 0.7225 0.0729 1.1255 a) The Geometric Mean. For average growth rates add 1 to each rate. 1 x g x1 x 2 x3 x n n n x 5 1.14 1.19 0.99 1.031.06 5 1.46632 1.46632 1 5 1.46632 0.2 1.07956 . So the average growth rate was 7.956%. b) The Harmonic Mean. 1 1 xh n 1 1 1 x 5 64 39 70 35 80 5 0.015625 0.0256410 0.014857 0.0285714 0.125000 1 1 0.0.0966232 5 1 1 1 0.0193246 . 1 So xh 1 1 n 1 x 1 51 .7474 . 0.0193246 14 251y0612 2/15/06 c) The Root-Mean-Square. 1 1 2 x rms x 2 0.10 2 0.34 2 0.37 2 0.26 2 0.85 2 0.27 2 n 6 1 1 0.0100 0.1156 0.1369 0.0676 0.7225 0.0729 1.1255 0.187583 6 6 . So x rms 1 n x 2 0.187583 0.43311 . d) (i) Geometric mean using natural logarithms 1 ln( x) 1 ln 1.14 ln 1.19 ln 0.99 ln 1.03 ln 1.06 ln x g n 5 1 1 0.131028 0.173953 0.010050 0.0295588 0.0582689 0.382759 0.0765518 5 5 So x g e 0.0765518 1.07956 . (ii) Geometric mean using logarithms to the base 10 1 log( x) 1 log 1.14 log 1.19 log 0.99 log 1.03 log 1.06 log x g n 5 1 1 0.0569049 0.0755470 0.0043648 0.0.0128372 0.0.0253059 0.166230 0.0332460 5 5 So x g 10 0.0332460 1.07956 15 251y0612 2/15/06 Programs used to Analyze Grouped Data #grp.mtb #Put frequencies in column 1 ‘f’ #and midpoints on column 2 ‘x’ let c3=c1*c2 let c4=c3*c2 let c5=c4*c2 name k1 'n' name k2 'mean' name k3 'Sfx' name k4 'Sfx2' name k5 'Sfx3' name k7 'Sfx^' name k8 'Sfx^2' name k9 'Sfx^3' let k1=sum(c1) let k3=sum(c3) let k4=sum(c4) let k5=sum(c5) let k2=k3/k1 print c10, c1-c5 print k1-k5 let c6=c2-k2 let c7=c1*c6 let c8=c7*c6 let c9=c8*c6 let k7 =sum(c7) let k8 = sum(c8) let k9 = sum(c9) print c10, c6-c9 print k7-k9 end #grpv.mtb let k6=k1-1 name k10 'var1' name k11 'var2' name k17 'stdev' let k10=k8/k6 let k11=k1*k2*k2 let k11=k4-k11 let k11=k11/k6 let k17=sqrt(k11) end #groups.mtb let k12=k6-1 let k13=k1/k6 let k13=k13/k12 let k14=k13*k9 let k15=2*k1*k2*k2*k2 let k16=3*k2*k4 let k15=k5-k16+k15 let k16=k13*k15 let k18=k16/k11 let k18=k18/k17 let k19=k14/k11 let k19=k19/k17 print k1-k19 end 16 251y0612 2/16/06 Processing of Original Data ————— 2/15/2006 4:29:58 PM ———————————————————— Welcome to Minitab, press F1 for help. Results for: 251x0601-1.MTW MTB > sum c1 Sum of f Sum of f = 153 MTB > print c10 c1 c11 c2 Data Display Row 1 2 3 4 5 6 7 8 9 Class -.95 to -.76 -.75 to -.56 -.55 to -.36 -.35 to -.16 -.15 to .04 .05 to .24 .25 to .44 .45 to .64 .65 to .84 f 1 2 9 25 65 35 10 5 1 bigF 1 3 12 37 102 137 147 152 153 #Original Numbers x -0.85 -0.65 -0.45 -0.25 -0.05 0.15 0.35 0.55 0.75 MTB > Save "C:\Documents and Settings\rbove\My Documents\Minitab\251x06011.MTW"; SUBC> Replace. Saving file as: 'C:\Documents and Settings\rbove\My Documents\Minitab\251x0601-1.MTW' Existing file replaced. MTB > let c12 = c11/153 MTB > let c13 = c1/153 MTB > print c10 c1 c13 c11 c12 Data Display Row 1 2 3 4 5 6 7 8 9 Class -.95 to -.76 -.75 to -.56 -.55 to -.36 -.35 to -.16 -.15 to .04 .05 to .24 .25 to .44 .45 to .64 .65 to .84 #Relative Frequencies f 1 2 9 25 65 35 10 5 1 frel 0.006536 0.013072 0.058824 0.163399 0.424837 0.228758 0.065359 0.032680 0.006536 bigF 1 3 12 37 102 137 147 152 153 bigFrel 0.00654 0.01961 0.07843 0.24183 0.66667 0.89542 0.96078 0.99346 1.00000 MTB > Execute "C:\Documents and Settings\rbove\My Documents\Minitab\grp.mtb" 1. Executing from file: C:\Documents and Settings\rbove\My Documents\Minitab\grp.mtb 17 251y0612 2/16/06 Data Display Row 1 2 3 4 5 6 7 8 9 Class -.95 to -.76 -.75 to -.56 -.55 to -.36 -.35 to -.16 -.15 to .04 .05 to .24 .25 to .44 .45 to .64 .65 to .84 f 1 2 9 25 65 35 10 5 1 x -0.85 -0.65 -0.45 -0.25 -0.05 0.15 0.35 0.55 0.75 #Table using computational method fx -0.85 -1.30 -4.05 -6.25 -3.25 5.25 3.50 2.75 0.75 fxsq 0.7225 0.8450 1.8225 1.5625 0.1625 0.7875 1.2250 1.5125 0.5625 fxcu -0.614125 -0.549250 -0.820125 -0.390625 -0.008125 0.118125 0.428750 0.831875 0.421875 Data Display n mean Sfx Sfx2 Sfx3 153.000 -0.0225490 -3.45000 9.20250 -0.581625 Data Display Row 1 2 3 4 5 6 7 8 9 Class -.95 to -.76 -.75 to -.56 -.55 to -.36 -.35 to -.16 -.15 to .04 .05 to .24 .25 to .44 .45 to .64 .65 to .84 #Column Sums x^ -0.827451 -0.627451 -0.427451 -0.227451 -0.027451 0.172549 0.372549 0.572549 0.772549 Data Display Sfx^ Sfx^2 Sfx^3 -0.000000000 9.12471 0.0373887 #Table using definitional method fx^ -0.82745 -1.25490 -3.84706 -5.68627 -1.78431 6.03922 3.72549 2.86275 0.77255 fx^sq 0.68468 0.78739 1.64443 1.29335 0.04898 1.04206 1.38793 1.63906 0.59683 fx^cu -0.566535 -0.494048 -0.702913 -0.294173 -0.001345 0.179807 0.517071 0.938443 0.461082 #Column sums MTB > exec 'grpv' Executing from file: grpv.MTB MTB > exec 'grps' Executing from file: grps.MTB Data Display n mean Sfx Sfx2 Sfx3 K6 Sfx^ Sfx^2 Sfx^3 var1 var2 K12 K13 k31 K15 k32 stdev g11 g12 153.000 -0.0225490 -3.45000 9.20250 -0.581625 152.000 -0.000000000 9.12471 0.0373887 0.0600310 0.0600310 151.000 0.00666609 0.000249236 0.0373887 0.000249236 0.245012 0.0169453 0.0169453 #Final results MTB > Save "C:\Documents and Settings\rbove\My Documents\Minitab\251x06011.MTW"; SUBC> Replace. 18 251y0612 2/16/06 Saving file as: 'C:\Documents and Settings\rbove\My Documents\Minitab\251x0601-1.MTW' Existing file replaced. MTB > print gr Data Display #Percent Data for Geometric mean. gr 5 MTB MTB MTB MTB > > > > 10 let let let let -1 c15 c16 c17 c18 = = = = 3 6 c15/100 c15+1 loge(c16) logten(c16) MTB > sum c17 Sum of lngrf Sum of lngrf = 0.221878 MTB > mean c17 Mean of lngrf Mean of lngrf = 0.0443755 MTB > let k17 = mean(c17) MTB > let k17 = expon(k17) MTB > print k17 Data Display k17 1.04537 MTB > sum c18 Sum of loggrf Sum of loggrf = 0.0963603 MTB > mean c18 Mean of loggrf Mean of loggrf = 0.0192721 MTB > let k18 = mean(c18) MTB > let k18 = 10**k18 MTB > print k18 Data Display k18 1.04537 MTB > let k16 = c16(1)*c16(2)*c16(3)*c16(4)*c16(5) MTB > print k16 Data Display k32 1.24842 MTB > let k16 = k16**0.2 MTB > print k16 Data Display k32 1.04537 19 251y0612 2/16/06 MTB > print c19 Data Display mph 55 30 #Data for Harmonic mean 70 35 80 MTB > let c20 = 1/c19 MTB > sum c20 Sum of 1/mph Sum of 1/mph = 0.106872 MTB > mean c20 Mean of 1/mph Mean of 1/mph = 0.0213745 MTB > let k20 = mean(c20) MTB > let k20 = 1/k20 MTB > print k20 Data Display K20 46.7848 MTB > print c21 Data Display #Data for RMS y 0.01 0.25 0.37 0.26 0.85 0.27 MTB > let c22 = c21*c21 MTB > sum c22 Sum of ysq Sum of ysq = 1.0625 MTB > mean c22 Mean of ysq Mean of ysq = 0.177083 MTB > let k22 = mean(c22) MTB > let k22 = sqrt(k22) MTB > print k22 Data Display K22 0.420813 MTB > Print c15-c22 Data Display Row 1 2 3 4 5 6 gr 0.05 0.10 -0.01 0.03 0.06 grf 1.05 1.10 0.99 1.03 1.06 lngrf 0.0487902 0.0953102 -0.0100503 0.0295588 0.0582689 loggrf 0.0211893 0.0413927 -0.0043648 0.0128372 0.0253059 mph 55 30 70 35 80 1/mph 0.0181818 0.0333333 0.0142857 0.0285714 0.0125000 y 0.01 0.25 0.37 0.26 0.85 0.27 ysq 0.0001 0.0625 0.1369 0.0676 0.7225 0.0729 Processing of Original Data with nines added to first two numbers. ————— 2/15/2006 6:34:07 PM ———————————————————— 20 251y0612 2/16/06 Welcome to Minitab, press F1 for help. Results for: 251x0601-2.MTW MTB > sum c1 Sum of f Sum of f = 171 MTB > print c10 c1 c11 c2 Data Display Row 1 2 3 4 5 6 7 8 9 Class -.95 to -.76 -.75 to -.56 -.55 to -.36 -.35 to -.16 -.15 to .04 .05 to .24 .25 to .44 .45 to .64 .65 to .84 #Original Numbers with nines added to frequencies f 10 11 9 25 65 35 10 5 1 bigF 10 21 30 55 120 155 165 170 171 x -0.85 -0.65 -0.45 -0.25 -0.05 0.15 0.35 0.55 0.75 MTB > Save "C:\Documents and Settings\rbove\My Documents\Minitab\251x06012.MTW"; SUBC> Replace. Saving file as: 'C:\Documents and Settings\rbove\My Documents\Minitab\251x0601-2.MTW' Existing file replaced. MTB > let c12 = c11/171 MTB > let c13 = c1/171 MTB > sum c13 Sum of frel Sum of frel = 1 MTB > print c10 c1 c13 c11 c12 Data Display Row 1 2 3 4 5 6 7 8 9 Class -.95 to -.76 -.75 to -.56 -.55 to -.36 -.35 to -.16 -.15 to .04 .05 to .24 .25 to .44 .45 to .64 .65 to .84 f 10 11 9 25 65 35 10 5 1 frel 0.058480 0.064327 0.052632 0.146199 0.380117 0.204678 0.058480 0.029240 0.005848 bigF 10 21 30 55 120 155 165 170 171 #Relative Frequencies bigFrel 0.05848 0.12281 0.17544 0.32164 0.70175 0.90643 0.96491 0.99415 1.00000 MTB > Execute "C:\Documents and Settings\rbove\My Documents\Minitab\grp.mtb" 1. Executing from file: C:\Documents and Settings\rbove\My Documents\Minitab\grp.mtb Data Display Row 1 2 3 4 5 6 7 8 9 Class -.95 to -.76 -.75 to -.56 -.55 to -.36 -.35 to -.16 -.15 to .04 .05 to .24 .25 to .44 .45 to .64 .65 to .84 f 10 11 9 25 65 35 10 5 1 x -0.85 -0.65 -0.45 -0.25 -0.05 0.15 0.35 0.55 0.75 fx -8.50 -7.15 -4.05 -6.25 -3.25 5.25 3.50 2.75 0.75 #Table using computational method fxsq 7.2250 4.6475 1.8225 1.5625 0.1625 0.7875 1.2250 1.5125 0.5625 fxcu -6.14125 -3.02088 -0.82013 -0.39063 -0.00813 0.11813 0.42875 0.83188 0.42188 21 251y0612 2/16/06 Data Display n mean Sfx Sfx2 Sfx3 171.000 -0.0991228 -16.9500 19.5075 -8.58038 Data Display Row 1 2 3 4 5 6 7 8 9 Class -.95 to -.76 -.75 to -.56 -.55 to -.36 -.35 to -.16 -.15 to .04 .05 to .24 .25 to .44 .45 to .64 .65 to .84 #Column Sums x^ -0.750877 -0.550877 -0.350877 -0.150877 0.049123 0.249123 0.449123 0.649123 0.849123 fx^ -7.50877 -6.05965 -3.15789 -3.77193 3.19298 8.71930 4.49123 3.24561 0.84912 fx^sq 5.63817 3.33812 1.10803 0.56910 0.15685 2.17218 2.01711 2.10680 0.72101 Data Display Sfx^ Sfx^2 Sfx^3 #Table using definitional method fx^cu -4.23357 -1.83890 -0.38878 -0.08586 0.00770 0.54114 0.90593 1.36757 0.61223 #Column sums -0.000000000 17.8274 -3.11254 MTB > exec 'grpv' Executing from file: grpv.MTB MTB > exec 'grps' Executing from file: grps.MTB Data Display n mean Sfx Sfx2 Sfx3 K6 Sfx^ Sfx^2 Sfx^3 var1 var2 K12 K13 k31 K15 k32 stdev g11 g12 #Final results 171.000 -0.0991228 -16.9500 19.5075 -8.58038 170.000 -0.000000000 17.8274 -3.11254 0.104867 0.104867 169.000 0.00595197 -0.0185257 -3.11254 -0.0185257 0.323832 -0.545529 -0.545529 MTB > print gr #Percent Data for Geometric mean divided by 100 Data Display gr 0.14 MTB MTB MTB MTB > > > > let let let sum 0.19 -0.01 0.03 0.06 c16 = c15+1 c17 = loge(c16) c18 = logten(c16) c17 Sum of lngrf Sum of lngrf = 0.382759 MTB > mean c17 Mean of lngrf Mean of lngrf = 0.0765518 22 251y0612 2/16/06 MTB > let k17 = mean(c17) MTB > let k17 = expon(k17) MTB > print k17 Data Display K17 1.07956 MTB > sum c18 Sum of loggrf Sum of loggrf = 0.166230 MTB > mean c18 Mean of loggrf Mean of loggrf = 0.0332460 MTB > let k18 = mean(c18) MTB > let k18 = 10**k18 MTB > print k18 Data Display K18 1.07956 MTB > let k16 = c16(1)*c16(2)*c16(3)*c16(4)*c16(5) MTB > print k16 Data Display K18 1.46632 MTB > let k16 = k16**0.2 MTB > print k16 Data Display K16 1.07956 MTB > print c19 Data Display mph 64 39 #Data for Harmonic mean 70 35 80 MTB > let c20 = 1/c19 MTB > sum c20 Sum of 1/mph Sum of 1/mph = 0.0966232 MTB > mean c20 Mean of 1/mph Mean of 1/mph = 0.0193246 MTB > let k20 = mean(c20) MTB > let k20 = 1/k20 MTB > print k20 Data Display K20 51.7474 23 251y0612 2/16/06 MTB > print c21 Data Display #Data for RMS y 0.10 0.34 0.37 0.26 0.85 0.27 MTB > let c22 = c21*c21 MTB > sum c22 Sum of ysq Sum of ysq = 1.1255 MTB > mean c22 Mean of ysq Mean of ysq = 0.187583 MTB > let k22 = mean(c22) MTB > let k22 = sqrt(k22) MTB > print k22 Data Display K22 0.433109 MTB > print c15 - c22 Data Display Row 1 2 3 4 5 6 gr 0.14 0.19 -0.01 0.03 0.06 grf 1.14 1.19 0.99 1.03 1.06 lngrf 0.131028 0.173953 -0.010050 0.029559 0.058269 loggrf 0.0569049 0.0755470 -0.0043648 0.0128372 0.0253059 mph 64 39 70 35 80 1/mph 0.0156250 0.0256410 0.0142857 0.0285714 0.0125000 y 0.10 0.34 0.37 0.26 0.85 0.27 ysq 0.0100 0.1156 0.1369 0.0676 0.7225 0.0729 MTB > Save "C:\Documents and Settings\rbove\My Documents\Minitab\251x06012.MTW"; SUBC> Replace. Saving file as: 'C:\Documents and Settings\rbove\My Documents\Minitab\251x0601-2.MTW' Existing file replaced. 24