A school counselor tests the level of depression in fourth graders in a particular class of 20 students. The counselor wants to know whether the kind of students in this class differs from that of fourth graders in general at her school. On the test, a score of 10 indicates severe depression, while a score of 0 indicates no depression. From reports, she is able to find out about past testing. Fourth graders at her school usually score 5 on the scale, but the variation is not known. Her sample of 20 fiftsh graders has a mean depression score of 4.4.

Question

A school counselor tests the level of depression in fourth graders in a particular class of 20 students. The counselor wants to know whether the kind of students in this class differs from that of fourth graders in general at her school. On the test, a score of 10 indicates severe depression, while a score of 0 indicates no depression. From reports, she is able to find out about past testing. Fourth graders at her school usually score 5 on the scale, but the variation is not known. Her sample of 20 fiftsh graders has a mean depression score of 4.4.
Suppose the counselor tested the null hypothesis that fourth graders in this class were less depressed than those at the school generally. She figures her t scores to be -.20. What decision should she make regarding the null hypothesis?

PsyDAG · Answer

With infinite degrees of freedom, you need a t score of 1.96 to reject the null hypothesis at the .05 level. What does that tell you, if your t = -.20?

Kristen · Answer

Reject it.