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

Multiple Choice

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

A) 15 / 20 = 0.75
B) 15 / 19 = 0.79
C) 15² / 20 = 11.25
D) 15² / 19 = 11.84