A market research firm used a sample of individual to rate the purchase -potential of a particular product before and after the individuals saw a new television commercial about the product. The purchase potential ratings were based on a 0 to 10 scale, with higher values indicating higher purchase potential. The null hypotesis is stated that the mean ratings "after' would be less than or equal to the mean rating "before".
Individual 1 2 3 4 5 6 7 8
After 6 6 7 4 3 9 7 6
Before 5 4 7 3 5 8 5 6
a) carry out the an appropriate test (at 5% los) base on the above data, and infer whether the commercial has imporved the mean purchase rating.
b) Justify the choice of the test.