A cognitive psychologist believes that a particular drug improves short-term memory. The drug is safe, with no side effects. An experiment is conducted in which 8 randomly selected subjects are given...

A cognitive psychologist believes that a particular drug improves short-term memory. The drug is safe, with no side effects. An experiment is conducted in which 8 randomly selected subjects are given the drug and then given a short time to memorize a list of 15 words. The subjects are then tested for retention (i.e., their memory of the words) 15 minutes after the memorization period. The number of words correctly recalled by each subject is as follows:

Subject     Words Recalled

1                          9

2                          11

3                          12

4                          8

5                          10

6                          8

7                          6

8                          12

Over the past few years, the psychologist has collected a lot of data using this task with similar subjects. Although he has lost the original data, he remembers that the mean was 6 words correctly recalled and that the data were normally distributed.

1. On the basis of this data, what can we conclude about the effect of the drug on short-term memory? Use alpha = 0.01_2-tailedin making your decision. Be sure to state your hypotheses first.


2. Determine the size of effect and provide a proper interpretation of this value.