Exam 10: Two-Sample Hypothesis Tests

The table below compares two samples taken to compare the mean age of individuals who purchased the iPhone 3G at two AT&T store locations.Very briefly,what conclusions can you draw?

In comparing the means of two independent samples,if the test statistic indicates a significant difference at α =.05,it will also be significant at α = .10.

The table below shows the mean number of daily errors by seven 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 have decreased from Week 1 to Week 2. The right-tailed critical value at α = .05 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.To compare the pass rates,the pooled proportion would be

The Welch-Satterthwaite test is more conservative than the pooled variance test to compare two population means with unknown variances in independent samples.

Of 200 youthful gamers (under 18)who tried the new Z-Box-Plus game,160 rated it "excellent," compared with only 144 of 200 adult gamers (18 or over).The test statistic to test the two proportions for equality would be

The folded F-test for equality of variances

Of 200 youthful gamers (under 18)who tried the new Z-Box-Plus game,160 rated it "excellent," compared with only 144 of 200 adult gamers (18 or over).The p-value for a right-tailed test to compare the two proportions would be approximately

When using independent samples to test the difference between two population means,a pooled variance is used if the population variances are unknown and assumed equal.

In a random sample of patient records in Cutter Memorial Hospital,six-month postoperative exams were given in 90 out of 200 prostatectomy patients,while in Paymor Hospital such exams were given in 110 out of 200 cases.In a left-tailed test for equality of proportions,the test statistic is

In an F test for the ratio of two population variances,the degrees of freedom in both the numerator and the denominator must be equal.

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 pass rates,the p-value for a right-tailed test is approximately

We could use the same data set for two independent samples (i.e. ,two columns of data)either to compare the means (t-test)or to compare the variances (F test).

In a right-tailed test comparing two means with known variances,the sample sizes were n1 = 8 and n2 = 12.At α = .05,the critical value would be

Kate wants to compare two means.Her sample statistics were 1 = 22.7,s12 = 5.4,n1 = 9 and 2 = 20.5,s22 = 3.6,n2 = 9.Assuming equal variances,the degrees of freedom for his test will be

When the variances are unknown,a test comparing two independent sample means would use the Student's t distribution.