NAME: YOUR LETTER ANSWERS 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Note: When done, using the same naming format as your homework files, name this file as: b E270Lastname Firstname TEST5 and e-mail it back to stowfig@iupui.edu Next FOUR questions are related to the following data: The following is a random sample of n = 112 undergraduate student annual textbook expense. 270 290 620 670 780 250 410 440 500 770 240 460 460 750 200 350 440 600 590 710 460 730 740 400 590 540 600 470 650 690 790 490 720 610 420 440 730 490 750 220 530 260 520 250 570 480 440 260 550 220 480 250 250 780 790 600 500 300 590 610 440 240 420 230 330 350 770 320 780 500 220 390 360 680 590 320 570 570 390 320 790 760 760 580 760 330 750 570 690 220 250 620 580 360 390 790 270 800 1 a b c d The sample standard deviation is: 183.00 177.71 174.22 170.81 a b c d To build an interval estimate of the population mean, the standard error of the mean is, 14.87 16.30 17.29 18.95 a b c d The margin of error for a 95% interval estimate is, $29.10 $31.22 $33.89 $35.01 2 3 470 440 500 610 260 420 780 680 250 210 590 380 360 620 4 a b c d To reduce the margin of error in the previous question to 16, the sample size should be ________. Use the standard deviation of the current sample (rounded to the nearest integer) as the planning value. 400 422 475 503 a b c d In interval estimation of a population parameter, increasing the sample size would reduce the margin of sampling error, diminishing the error probability. reduce the margin of sampling error, making the interval estimate more precise. increase the margin of sampling error, making the interval estimate more precise. reduce the margin of sampling error, increasing the confidence level. 5 Next TWO questions are related To build a 95% interval estimate of the average commuting distance to the campus by IUPUI students, in a random sample of n = 128 students, the sample average distance was xx = 17.1 miles with a sample standard deviation of s = 7.5 miles. 6 The standard error of the mean for the interval is _____. a 1.099 b 0.928 c 0.764 d 0.663 7 a b c d We are 95% confident that average commuting distance for the population of IUPUI students is between: 14.0 20.2 14.9 19.3 15.8 18.4 16.3 17.9 a b c d As a class project, each of 220 students taking E270 is required to obtain a sample of n = 100 students and build a 95% confidence interval for the distance travelled to the campus. The instructor thus receives 200 different interval estimates. The instructor would expect _____ of these intervals to contain the population mean distance travelled. 209 200 190 110 95 10450 8 Next TWO questions are based on the follow sample data Assume the student commuting time to the IUPUI campus is normally distributed. To build a 95% confidence interval for the mean commuting time for all IUPUI students, a random sample of n = 5 students provided the following times (shown in minutes). x 10 25 15 30 20 9 a b c The sample variance is s = _____. 50 55.4 62.5 d 10 a b c d 11 a b c d 64 Given the above sample data, the lower and upper end of a 95% interval estimate of the mean commuting time of all IUPUI students is L = _____ and U = _____ minutes. 9.0 31.0 10.2 29.8 12.6 27.4 13.1 26.9 To obtain a 95% interval estimate for the mean student commuting time to the IUPUI campus with a margin of sampling error of MOE = 2 minutes, the minimum sample size should be n = _____. A pilot sample of students provided a planning value of = 9 minutes for the standard deviation. 78 67 62 55 Next THREE questions are related In a sample of n = 460 IUPUI undergraduate students polled x = 138 stated that they are planning to go to graduate graduate school. 12 The standard error of the sample proportion is a 0.0112 b 0.0162 c 0.0198 d 0.0214 13 a b c d 14 a b c d 15 a b c d The lower and upper end of a 90% confidence interval for the proportion of IUPUI undergraduate students who plan to go to graduate school are L = ______ and U = _____. 0.241 0.359 0.250 0.350 0.258 0.342 0.265 0.335 In the previous question, the margin of error for the interval so that in 19 out of 20 cases such intervals would contain the actual population proportion of IUPUI undergraduate student who plan to go to graduate school is, MOE = _______. 0.042 0.046 0.049 0.052 To build a 95% confidence interval, with a margin of error of MOE = 0.03, for the population proportion of IUPUI undergraduates who plan to go to graduate school, the minimum sample size is n = _____. Use a planning value of = 0.35. 920 972 1005 1016