©1998 Brooks/Cole Publishing/ITP

Similarly, the third and fourth variables, year and major, generate nonnumerical data. Year had four categories (Fr, So, Jr, Sr), and the major had one category for each undergraduate program major on campus. The last variable, current number of units enrolled, is numerically valued, generating a set of numbers rather than a set of qualities or characteristics.

Although we have discussed each variable individually, remember that we have measured each of these five variables on a single experimental unit: the student. Therefore, in the example, a “measurement” really consists of five observations, one for each of the five measured variables.

For example, the measurement taken on student 2 produces this observation:

(2.3, F, So, Mathematics, 15)