An advertisement is being tested to see if it is effective in creating the intended mood of

Question:

An advertisement is being tested to see if it is effective in creating the intended mood of relaxation. A sample of 15 people was tested just before and just after viewing the ad. Their questionnaire included many items, but the one being considered now is: Please describe your current feeling on a scale from 1 (very tense) to 5 (completely relaxed). The results are shown in Table 16.4.3.
a. How many people reported higher relaxation after viewing the ad than before? How many reported lower relaxation? How many were unchanged?
b.* Find the modified sample size.
c.* Perform the nonparametric sign test for the differences.
d. Briefly summarize this result in terms of the effect (if any) of the advertisement.