A cognitive psychologist believes that a particular drug improves short-term memory. An experiment is conducted in which 8 randomly selected participants are given the drug and then given a short time to memorize a list of 10 words. Participants are then tested for retention 15 minutes after the memorization period. The number of words correctly recalled by each participant is as follows: 8, 9, 10, 6, 8, 7, 9, 7. 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.

Required:
a. On the basis of these data, what can we conclude about the effect of the drug on short-term memory? Use α = 0.05.
b. Determine the size of the effect.