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Data & Analytics · Foundational

Levels of Measurement

The four scales of data: nominal (labels), ordinal (ordered categories), interval (equal spacing, no true zero) and ratio (equal spacing with a true zero).

Definition

The scale determines valid statistics: mode for nominal, median for ordinal, mean for interval, and ratios only for ratio data. Temperature in °C is interval, while Kelvin, weight and revenue are ratio.

Exam tip

Ratios such as 'twice as much' are valid only for ratio-scale data.

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