Levels of Measurements

Before you proceed, please download the practice sheet placed under “Materials” tab.

Nominal (Categorical, NOT Ordered)


  • Variable with limited number of possible mutually exclusive values or categories
  • Qualitative data with no intrinsic ordering to the categories.
  • Used for labelling (labelled data) without any quantitative value
  • Examples – Gender, Nationality

Ordinal (Categorical, Ordered)

It is similar to nominal with the difference that it has clear ordering of the categories

Exact difference between categories is not known.

Example – movie rating on a scale of 1-5 (note – 1 to 5 are not actual values but just notation or ranking), states ranking based on population

Interval (Numerical, NO True Zero)

Interval variables are numeric variables in which we know both the order and the exact differences between the values but they don’t have a “True Zero” or “Absolute Zero”

Example – Celsius temperature scale. Here zero (like 0 degrees Celsius) doesn’t mean the absence of value, but is actually just another number used on the scale 

Ratio (Numerical, with True Zero)

Ratio variables are numeric variables which have order, exact differences between the values and also have a Absolute or True zero.

Strongest form of measurement as can be meaningfully added, subtracted, multiplied and divided (ratios)

Example – Height, Weight, Length etc