Mike, a developmental psychologist, wants to know if overall life stress increase or decreases as working women get older.He obtains score on the index of Life Stress (ILS) from a group of 100 working women when they are 40 years old.He is able to obtain a second ILS from 45 of these women at age 60 to asses whether they felt significantly more or less stress as they grew older.The ILS consists of two scores, interpersonal life stress and occupation life stress. The two score combine to form an index of life stress.

The data file contains 45 cases, one for each woman, and four variables - their interpersonal life stress and occupational life stress at age 40 and their interpersonal and occupational life stress at age 60.

The question is:

1-Compute a score to obtain a total Index of Life Stress at age 40 for each woman.

2 - Compute a score to obtain a total Index of Life Stress at age 60 for each woman.

I am confused if I do the average or sum to compute the total index or if that is not how I do it at all!