Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Problems from Intro Stats by DeVeaux, Velleman and Bock Crossing Lake Ontario Between 1954 and 2003, swimmers have crossed Lake Ontario 43 times. Both women and men have made the crossing. A summary of the data regarding their times is as follows. Group Count Mean (min) Standard Deviation (min) female 22 1271.59 261.111 male 20 1196.75 304.369 What is the difference between average crossing times for female and male swimmers (out of all swimmers in the world) to cross the lake? Yogurt Is there a difference in calories between servings of strawberry and vanilla yogurt? How much? Brand Strawberry (cal) Vanilla (cal) America’s Choice 210 200 Breyer’s Lowfat 220 220 Columbo 220 180 Dannon Light ‘n’ Fit 120 120 Dannon Lowfat 210 230 Dannon LaCreme 140 140 Great Value 180 80 La Yogurt 170 160 Mountain High 200 170 Stonyfield Farm 100 120 Yoplait Custard 190 190 Yoplait Light 100 100 Normal temperature A researcher measured the body temperatures of a randomly selected group of adults. The data he collected are summarized below. a) Find a 98% confidence interval for the mean body temperature among all adults in the world. b) 98.6°F is commonly assumed to be “normal.” Do these data suggest otherwise? Explain. Count 50 Mean 98.285°F Median 98.200°F Standard deviation 0.6824°F Interquartile range 1.050°F Cuckoo eggs Cuckoos lay their eggs in the nests of other (host) birds. The eggs are then adopted and hatched by the host birds. But the potential host birds lay eggs of different sizes. Does the cuckoo use different length eggs for different foster species? Test this for two different species, using the data below to conduct a hypothesis test and compute a 95% confidence interval for the difference in mean egg length in the two species. Egg length for Sparrow Egg length for Robin Egg length for Wagtail (mm) (mm) (mm) 20.85 21.05 21.05 21.65 21.85 21.85 22.05 22.05 21.85 22.85 22.05 21.85 23.05 22.05 22.05 23.05 22.25 22.45 23.05 22.45 22.65 23.05 22.45 23.05 23.45 22.65 23.05 23.85 23.05 23.45 23.85 23.05 24.05 24.05 23.05 24.05 25.05 23.05 24.05 23.25 24.85 23.85 Doritos Some students checked 6 bags of Doritos marked with a net weight of 28.3 grams. They carefully weighed the contents of each bag, recording the masses (in grams): 29.2, 28.5, 28.7, 28.9, 29.1, 29.5. a) Test the company’s claim about the net weight. b) Compute a 95% confidence interval for the mean net weight of such bags of these chips. Job satisfaction A company institutes an exercise break for its workers to see if this will improve job satisfaction, as measured by a questionnaire. Scores for 10 randomly selected workers, each one measured before and after the implementation of the program, are shown. a) Find a 95% confidence interval for the mean of the differences in scores (after minus before). b) On average, is there a difference from before to after the implementation of the program? Worker number Before (unitless) After (unitless) 1 34 33 2 28 36 3 29 50 4 45 41 5 26 37 6 27 41 7 24 39 8 15 21 9 15 20 10 27 37