10. Hypothesis Testing for Two Samples

Which statement about the $F$-distribution is always true?

Two machines produce metal rods. You take independent random samples of their lengths (shown below) as part of a hypothesis test. Calculate the F statistic for this test.

Sample A: $s^2=2.1,n=10$

Sample B: $s^2=4.2,n=12$

In a two-sample Hypothesis Test for Variance, what does an $F$-statistic near 1 indicate?

F Test Statistic

a. If s2,1 represents the larger of two sample variances, can the F test statistic ever be less than 1?

F Test Statistic

b. Can the F test statistic ever be a negative number?

F Test Statistic

c. If testing the claim that sigma2,1 is not equals to sigma2,2 what do we know about the two samples if the test statistic F is very close to 1?

Test for Normality For the hypothesis test described in Exercise 2, the sample sizes are n1 = 2208 and n2 = 1986 When using the F test with these data, is it correct to reason that there is no need to check for normality because both samples have sizes that are greater than 30?