Question

Solution for a question from Statistics for the Behavioral Sciences, by Susan Nolan & Thomas Heinzen, 9781464155130​.

Teaching assistants, race, and standard deviations: Researchers reported that the race of the teaching assistants (TAs) for a class had an effect on student outcome (Lusher, Campbell, & Carrell, 2015). They reported that “Asian students receive a 2.3% of a standard deviation increase in course grade when the racial composition of the TAs is entirely Asian. Similarly, non-Asian students see a 3.7% of a standard deviation increase in course grade when enrolled in a class with all non-Asian TAs.” They hypothesized several reasons for this effect, including that students may see TAs of a similar race as inspiring or may simply be more comfortable learning from someone of the same race. Knowing what you know about standard deviations, explain this finding in your own words. Also, state whether this is a large effect, and explain your answer.

Answer 1

Let's assume that in this research 100 students of each category were studied for their grades, and the grading is done out of a total of 100 marks.

In this case a reasonably fair assumption for a standard deviation is around 10 to 20.

So assuming the standard deviation as S = 15 for both the categories:

Increase in the course grade for Asian students = 2.3% of a standard deviation = 2.3% of 15 = 0.345

Increase in the course grade for non-Asian students = 3.7% of a standard deviation = 3.7% of 15 = 0.555

Thus we see that the increase is higher for non-Asian students, based on the assumption that the standard deviation for both these groups is same and equal to 15.

Thus, talking practically, this change is not very large, because the grading is done from 100 marks.

Hope this helps !