Question

Suppose researchers are interested in the relationship between systolic blood pressure and periodontal disease in a population of low-income families. In order to address the relationship most efficiently, the researchers have decided to model age as a potential confounding variable. During the analysis phase of their investigation, the researchers found it most appropriate to model age as a dummy variable. The variable was quantified in quartiles, and grouped in the following manner.

Category1) Age<25

Category2) Age (25, 35)

Category3) Age (36, 45)

Category4) Age >45

The reference category to which each of the others will be compared is : Age>45

Complete the following table and organize these categories into a set of dummy variables. Describe what a 1 and 0 indicate for each dummy variable.

	X1
Age<25						X1: 1 if

Answer 1