Comparing Means

Cross tabulation is a useful way of exploring the relationship between variables that contain only a few categories.  For example, for example in GSS2000, we could compare how men and women feel about abortion.  Here our dependent variable (abortion) consists of only two categories—approve or disapprove. But what if we wanted to find out if the average age at birth of first child is younger for women than for men?  Here our dependent variable is a continuous variable consisting of many values.  We could recode it so that it only had a few categories (e.g., under 20, 20 to 24, 25 to 29, 30 to 34, 35 to 39, 40 and older), but that would result in the loss of a lot of information.  A better way to do this would be to compare the mean age at birth of first child for men and women.

We're going to use the subset from the 2000 General Social Survey to answer this question.  Click on "Analyze", point your mouse at "Compare Means", and then click on "Means".  We want to put age at birth of first child (AGEKDBRN) in the Dependent List and SEX in the Independent List.  Highlight AGEKDBRN in the list of variables on the left of your screen, and then click on the arrow next to the Dependent List box.  Now click on the list of variables on the left and use the scroll bar to find the variable SEX.  Click on it to highlight it and then and then click on the arrow next to the Independent List box.  On the average, women are a little more than two years younger than men at the birth of first child.