Exam 10: Two-Sample Hypothesis Tests

The table below shows two samples taken to compare the mean age of individuals who purchased the iPhone 3G at two AT&T store locations. At α = .05,can you conclude that the first sample has a larger variance than the second sample?

Does the Speedo Fastskin II Male Hi-Neck Bodyskin competition racing swimsuit improve a swimmer's 200-yard individual medley performance times? A test of 100 randomly chosen male varsity swimmers at several different universities showed that 66 enjoyed improved times,compared with only 54 of 100 female varsity swimmers.To test for equality in the proportions of men versus women who experienced improvement,the test statistic is approximately

A random sample of Ersatz University students revealed that 16 females had a mean of $22.30 in their wallets with a standard deviation of $3.20,while 6 males had a mean of $17.30 with a standard deviation of $9.60.At α = .10,to test for equal variances in a two-tailed test,the critical values are

The z-test for zero difference in two means

Mary analyzed occupancy rates at two community hospitals and obtained the following Excel results. Which conclusion is correct in a two-tailed test at α = .05?

A corporate analyst is testing whether mean inventory turnover has increased.Inventory turnover in six randomly chosen product distribution centers (PDCs)is shown. The value of the test statistic is

The table below shows the mean number of daily errors by air traffic controller trainees during the first two weeks on the job.We want to perform a paired t-test at α = .05 to see if the mean daily errors decreased significantly. The test statistic is

At Huge University,a sample of 200 business school seniors showed that 26 planned to pursue an MBA degree,compared with 120 of 800 arts and sciences seniors.We want to know if the proportion is higher in the arts and sciences group.The pooled proportion for this test is

Two well-known aviation training schools are being compared using random samples of their graduates.It is found that 70 of 140 graduates of Fly-More Academy passed their FAA exams on the first try,compared with 104 of 260 graduates of Blue Yonder Institute.The test statistic to test the pass rates for equality is

The F distribution is never negative and is always skewed right.

A corporate analyst is testing whether mean inventory turnover has increased.Inventory turnover in six randomly chosen product distribution centers (PDCs)is shown. The right-tailed critical value at α = 0.005 is

Random samples of students were compared to see whether or not there was a difference in the proportion favoring the university's proposed switch from MWF (three-day)classes to MW and TR (two-day)classes.The results shown below are from MegaStat.Analyze these results thoroughly.

When testing the difference between two population proportions,it is necessary to use the same size sample from each population.

Carver Memorial Hospital's surgeons have a new procedure that they think will decrease the variance in the time it takes to perform an appendectomy.A sample of 8 appendectomies using the old method had a variance of 36 minutes,while a sample of 10 appendectomies using the experimental method had a variance of 16 minutes.At α = .10 in a two-tailed test for equal variances,the critical values are

Based on a random sample of 13 tire changes,the mean time to change a tire on a Boeing 777 has a mean of 59.5 minutes with a standard deviation of 8.4 minutes.For 10 tire changes on a Boeing 787,the mean time was 64.3 minutes with a standard deviation of 12.4 minutes.To test for equal variances in a two-tailed test at α = .10,the critical values are

Litter sizes (number of pups)for randomly chosen dogs from two breeds were compared.The sample data were entered into Excel,and the following results were produced. What is the p-value for a left-tailed test comparing the means at α = .05?

If the sample proportions are p1 = 15/60 and p2 = 20/90,normality may be assumed in a test comparing the two population proportions.

Which of the following is not a characteristic of the F distribution?

Two well-known aviation training schools are being compared using random samples of their graduates.It is found that 70 of 140 graduates of Fly-More Academy passed their FAA exams on the first try,compared with 104 of 260 graduates of Blue Yonder Institute.To compare the two proportions,the assumption of normality of the test statistic is

A paired t-test with two columns of 8 observations in each column would use d.f.= 7.