Kinds of Variables

We will distinguish three different kinds of variables. Many more are possible, but for our purposes this will be sufficient.

  1. Interval Variables: A measurement of something where the relationship among values is clearly defined in a quantitative manner. Can say that one level is a mathematically defined function of another.

      Height, Income, Percent time spent studying.

      An income of $10000 is twice that of an income of $5000.

  2. Ordinal Variables: A qualitative assessment of something where the relationship among levels of the variable is known but only in a qualitative manner.

      Ranks of things like preferences for physical attributes in possible mates.

  3. Nominal Variables: Qualitative assessment of something where relationship among values of the variable is unknown.

      Sex, ethnicity, religious affiliation.

All levels of the variable must be mutually exclusive. That is, a person cannot belong to more than one level of income or to more than one sex.

Latent vs. Manifest Variables: