School psychologist is using a depression inventory on which a score of 0 indicates no depression and a score of 10 indicates severe depression to see if the level of depression in fourth graders in a particular class of 20 students differs from that of fourth graders in general at a school. based on the results of previous testing, fourth graders at the school usually have a score of 5 on the scale, but the variation is unknown. the current sample of 20 fifth graders has a mean depression score of 4.4.the psychologist tests the null hypothesis that the level of depression of fourth graders in this class does not differ from fourth graders in general at the school and obtains a t score of -.20. the decision regarding the null hypothesis would be to