levels of measurement

Levels of Measurement

A hierarchy of data precision that determines which statistical tests can be performed.

Nominal Data

Data that is sorted into named categories or labels (e.g., 'Yes' or 'No').

Ordinal Data

Data that is ranked or put in order, but the gaps between ranks are unequal or unknown (e.g., a 1-10 happiness scale).

Interval Data

Data measured using fixed, equal units where the distance between points is standardized (e.g., Temperature in Celsius).

Ratio Data

The most precise level of measurement, featuring equal units and a true zero point (e.g., weight, time, or distance).

True Zero

A point where none of the variable exists; required for Ratio data but not Interval data.

Subjectivity

A weakness of Ordinal data, as one person's '7/10' pain may be different from another person's '7/10'.

Frequency Data

Another name for Nominal data, as it simply counts how often something occurs in a category.

Quantitative Data

Numerical data which includes Ordinal, Interval, and Ratio levels of measurement.

Parametric Tests

Advanced statistical tests that require data to be at an Interval or Ratio level to be used.