CORRELATES OF REACTIVITY - PROBLEMS WITH REGRESSION-BASED METHODS

Computer simulations were used to compare change score and regression methods for identifying relationships between a third variable and reactivity. When the third variable was not correlated with baseline, the two methods were equally effective for detecting relationships between the third variable and change. However when there was a correlation between the third variable and baseline, regression measures of change yielded a high rate of Type one errors. Regression methods also had less power for detecting a relationship between the third variable and change when the relationship was in the direction opposite to the sign of the correlation with baseline. The implication of these findings for two areas of research are discussed: the relationship of fitness to heart rate reactivity and the relationship of hypertension to blood pressure reactivity.