Mental imagery has been shown to be very effective for improving memory. In one demonstration study, two groups of participants were presented with a list of 20 words. One group was given instructions to use mental images to help them remember the words, and the second group was given no special instructions. After the list was presented, each person was asked to recall as many words as possible. The scores for the two groups are as follows:

Imagery group: 18, 19, 18, 17, 19, 13, 20, 17, 18, 18, 20, 18, 14, 19, 16
No-instruction group: 11, 12, 16, 12, 10, 13, 14, 12, 10, 8, 13, 10, 11, 14, 12

a. (Using both Excel and SPSS) Create a histogram showing the distribution of scores for each group (two separate graphs).
b. Based on the appearance of the two distributions, what does the effect of using mental imagery appear to be on the level of performance for this memory task?