Section 1.2 Measurement Scales
In creating statistical measures, you might want to consider one of the following general types.Nominal measures - In this case, data falls into mutually exclusive and exhaustive categories for which the numerical value is only used for identification purposes. For example, assigning Male = 1, Female = -1.
Ordinal measures - In this case, data consists of discrete numerical values which can be ranked from lowest to highest or vice versa. For example, your grades in a number of classes are used to compute your GPA--which is a single number.
Interval measures - In this case, data possesses an order and where the distance between data values is of significance. For example, heights and weights.
Ratio measures - In this case, data can be expressed as a position in some interval and where ratios between observations have meaning. For example, percentile rankings