Logistic Regression Using SAS®: Theory and Application

4.3. A Three-Way Table

As we’ve just seen, using GENMOD to estimate a logit model for a 2 × 2 table doesn’t tell you much more than you would get with PROC FREQ. But with a 3-way table, things get more interesting.

Consider Table 4.2, which shows the cross classification of race, gender, and occurrence of sexual intercourse for a national sample of 15- and 16-year-olds, reported by Morgan and Teachman (1988).

Table 4.2. Race by Gender by Sexual Intercourse

		Intercourse
Race	Gender	Yes	No
White	Male	43	134
	Female	26	149
Black	Male	29	23
	Female	22	36

Let’s analyze Table 4.2 as a logit model, with intercourse as the dependent variable and race and sex as independent variables. Using the events/trials syntax in GENMOD, we have:

DATA interco; INPUT white male yes ...