A psychologist is studying the effects of various drugs on the speed of mental arithmetic. In an ...

A psychologist is studying the effects of various drugs on the speed of mental arithmetic. In an exploratory study, 32 subjects are divided equally into four drug conditions, and each subject solves as many problems as he or she can in 10 minutes. The mean number of problems solved follows for each drug group, along with the standard deviation.

Marijuana

Amphetamine

Valium

Alcohol

_

X

7

8

5

4

s

3.25

3.95

3.16

2.07