Study results indicate that the mean time to download a certain program to a personal computer is between 28.7 and 33.5 seconds. What is the study's margin of error? Question 15 options: 7.0 s 4.8 s 3.5 s 2.4 s Movie theater tickets in a region have a mean cost of $8.41 and a standard deviation of $0.82. What is the approximate standard deviation of the sampling distribution of the mean for samples of size 50? Question 16 options: $0.12 $0.17 $0.10 $0.02 In a random sample of 60 people who rode a roller coaster one day, the mean wait time is 42.4 minutes with a standard deviation of 8.8 minutes. In a random sample of 30 people who rode a Ferris wheel the same day, the mean wait time is 12.7 minutes with a standard deviation of 2.8 minutes. Which interval is the 99% confidence interval for the difference between the mean wait times of everyone who rode both rides? Question 17 options: In a simple random sample of 80 patients who saw a certain dentist, 9 patients had their teeth whitened. Which interval is the 95% confidence interval for the percent of all the dentist's patients who had their teeth whitened? Question 18 options: Which phrase is the best description of the association between variables X and Y? Question 19 options: weak positive association strong positive association strong negative association weak negative association Question 20 options: -2.5 2 2.5 -2