To examine the effect of exercise on body composition, data were collected from a sample of active women who engaged in 9 hours or more of physical activity per week (“ Effects of Habitual Physical Activity on the Resting Metabolic Rates and Body Composition of Women Aged 35 to 50 Years,” Journal of the American Dietetic Association [ 2001]: 1181– 1191). Percent of body fat was measured for each woman. The researchers planned to use the resulting data to learn about mean percent body fat for active women.