A high school counselor wanted to know if tenth-graders at her high school tend to have more free time than the twelfth-graders. She took random samples of 30 tenth-graders and 25 twelfth-graders.Each student was asked to record the amount of free time he or she had in a typical week. The mean for the tenth-graders was found to be 30 hours of free time per week with a standard deviation of 7.0 hours. For the twelfth-graders, the mean was 26 hours of free time per week with a standard deviation of 6.2 hours.

A. Make a 95% confidence interval for the difference between the corresponding population means.

Confidence interval:(______ , _____ )

B. Test at the 5% significance level whether the two population means are different.

Result: Given the above information, we find that ___________________________________ .