A researcher is interested in studying changes in marital
satisfaction over the course of marriage. She hypothesizes that
marital satisfaction is highest when couples are newly married,
that it decreases during the middle years of marriage, but rises
again during later years of marriage. In order to test her
hypothesis, she recruits fifty married couples within each of the
following conditions: (1) married less than 10 years; (2) married
15-20 years; (3) married more than 25 years. All 150 couples (50
from each condition) complete a standardized measure of marital
satisfaction