Descriptive Statistics > Scales of Measurement / Level of Measurement
The Four Scales of Measurement
Data can be classified as being on one of four scales: nominal, ordinal, interval or ratio. Each level of measurement has some important properties that are useful to know. For example, only the ratio scale has meaningful zeros.1. Nominal Scale. Nominal variables (also called categorical variables) can be placed into categories. They don’t have a numeric value and so cannot be added, subtracted, divided or multiplied. They also have no order; if they appear to have an order then you probably have ordinal variables instead.
For more, see: What is the Nominal Scale?
For more, see: What is the Ordinal Scale?
3. Interval Scale. An interval scale has ordered numbers with meaningful divisions. Temperature is on the interval scale: a difference of 10 degrees between 90 and 100 means the same as 10 degrees between 150 and 160. Compare that to high school ranking (which is ordinal), where the difference between 1st and 2nd might be .01 and between 10th and 11th .5. If you have meaningful divisions, you have something on the interval scale.
For more, see: What is the Interval Scale?
For more, see: What is the Ratio Scale?
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