Table 2.

Levels of measurement provided by data and appropriate statistical techniques

	Level of measurement
	Categorical		Quantitative
Type of data:	Nominal	Ordinal	Interval	Ratio
Characteristics	Qualitative (unordered)	Hierarchical (rank)	Equal intervals (rank) (equal intervals)	Equal ratios (rank) (equal intervals) (includes zero)
Examples	Gender (male, female)	Preference (first, second, third)	Temperature (15°C)	Age in years (20)
		Individual Likert items	Interrelated items comprising Likert scale
Appropriate statistics
Distribution	Nonparametric		Parametric
Central tendency	Mode	Median	Mean/SD
Analysis methods	Inferential categorical data analysis, Fisher's exact test		IRT, ANOVA, t tests, regression