Example. In a weight-loss study, suppose the weights of several people are measured each week for five weeks. In the data file, each person is a subject or case. The weights for the weeks are recorded in the variables weight1, weight2, and so on. The gender of each person is recorded in another variable. The weights, measured for each subject repeatedly, can be grouped by defining a within-subjects factor. The factor could be called week, defined to have five levels. In the main dialog box, the variables weight1, ..., weight5 are used to assign the five levels of week. The variable in the data file that groups males and females (gender) can be specified as a between-subjects factor to study the differences between males and females.