A telephone company representative estimates that 40% of its customers use voice mail. To test this hypothesis, she selected a sample of 100 customers and found that 37 used voice mail. At a standard deviation of 0.01, is there enough evidence to show the proportion differs from 40%?

Answer 1

Null hypothesis:
p = .40

Alternate hypothesis:
p does not equal .40

You can use a one-sample proportional z-test for your data. (Test sample proportion = .37 and sample size = 100) Find the critical value in the appropriate table at .01 level of significance for a two-tailed test. Compare the test statistic you calculate to the critical value from the table. If the test statistic exceeds the critical value, reject the null. If the test statistic does not exceed the critical value, do not reject the null. You can draw your conclusions from there.