12. A study was done of personality characteristics of 100 students who were tested at the beginning and end of their first year of college. The researchers reported the results in the following table:

(a) Focusing on the difference scores, figure the t values for each personality scale. (Assume that SD in the table is for what we have called S, the unbiased estimate of the population standard deviation.)

(b) Explain to a person who has never had a course in statistics what this table means