A 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. The results of previous testing indicate that 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.
-If the unbiased estimate of the population's variance is 15,the variance of the distribution of means is

Question

Quizplus · Accepted Answer

The variance of the distribution of means, also known as the standard error of the mean squared, is calculated by dividing the population variance by the sample size. Here, the population variance is given as 15, and the sample size is 20, so the variance of the distribution of means is 15 / 20 = 0.75.

A School Psychologist Is Using a Depression Inventory—on Which a Score