Chapter 9. Testing Differences

If the null hypothesis states that there is no difference between the mean income of males and the mean income of females, then the test is one-tailed. 

• True

• False

If the null hypothesis states that there is no difference between the mean net income of retail stores in Chicago and New York City, then the test is two-tailed. 

• False

• True

When the standard deviations are unknown and variances unequal, a test for the differences between two population means has n - 1 degrees of freedom. 

• True

• False

If two dependent samples of size 20 are used to test the difference between the means, the degrees of freedom for a t-statistic are 19. 

• True

• False

When testing for a difference between the means of two dependent samples the sample test statistic is a

If a hypothesis states that one population mean is greater than another population mean, then the test is _______________. 

Which condition must be met to conduct a test for the difference in two sample means using a z-statistic? 

• Data must be at least of nominal scale

• Populations must be normal

• Standard deviations of the two populations must be known

• Samples are dependent

Administering the same test to a group of 15 students and a second group of 15 students to see which group scores higher is an example of 

•  a one sample test of means.

• a two sample test of means.

• a test of proportions.

• a paired t-test.

For a hypothesis comparing two population means, what is the critical value for a one-tailed hypothesis test, using a 5% level of significance level, with both sample sizes equal to 13? The standard deviations for the samples are 5 and 7. Assume the population standard deviations are unequal. 

• 2.064

• 1.711

• 2.074

• 1.717

To test that the two groups of customers have equal savings rates, what is the critical value of z using a = 0.05?