We will distinguish three different kinds of variables. Many more
are possible, but for our purposes this will be sufficient.
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.
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.
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:
Latent Variables: These are the theoretical dependent and
independent variables that you wish to measure.
Manifest Variables: These are the things that you actually
measure.
The goal is to achieve convergence between your manifest and your
latent variables to the degree that it is possible.
