1. Nominal - most basic level, variables that are discrete & noncontinuous, Demographic data
2. Ordinal - 2nd Level, variables are assessed incrementally (pain scale, ability to perform ADL's,
worst to best, youngest to oldest)
3. Interval - 3rd level - ranking of order, distance between numeric values, can be measured on a scale (continuous variables)
4. Ratio - 4th & highest level - a scale with an absolute zero in the scale.