Читать книгу Interpreting and Using Statistics in Psychological Research - Andrew N. Christopher - Страница 43

A nominal scale is a measurement that divides people, objects, or events into categories according to their similarities or differences. It identifies which category an entity falls into. A nominal scale is the simplest kind of measurement scale because people, objects, or events of the same category are assigned the same number, and those of a different category get different numbers. For example, if we did a nationwide survey of college students, you might ask them what college or university they attend, whether they attend that school full time or part time, their political affiliation, and their class standing. These would be examples of nominal data. A student generally attends only one college or university and can be only a first-year, sophomore, junior, or senior.

Nominal scale: categorical data.

We can assign numbers to the different categories (which are often called “levels”) of a nominal variable. For example, for the variable of enrollment status (full time or part time), we can label students attending full time as “0” and those attending part time as “1.” Realize, though, that these numbers carry no meaning and are arbitrary. Obviously, students attending college full time are not somehow “less than” students attending part time. To take another example, I wore the number 44 on my jersey when I played football in high school. That does not mean I was twice as good a player as the person who wore number 22 on my team. In reality, jersey numbers identified positions that people played on their teams.

Photo 2.2 Is the player on the right better than the player on the left?

Source: ©iStockphoto.com/cstewart

With nominal data, we can form what are called frequency distributions; calculate certain statistics, such as the mode; and perform what is called a chi-squared test to help us make sense of this type of data. Chapters 3, 4, and 15 will help us use nominal data.