Classifying Data Types & Levels of Measurement

Qualitative (Categorical)

Labels, words, categories, preferences (e.g., shirt color, political party)

Quantitative Discrete

Numerical counts; whole numbers with gaps (e.g., number of books, dental cavities).

Quantitative Continuous

Numerical measurements that can take any value, including decimals (e.g., distance, time, height)

Nominal

Categories/names only; no natural order (e.g., comic book titles)

Ordinal

Ordered/ranked categories, but differences aren't meaningful (e.g., Agree / Disagree scales)

Interval

Ordered numbers where differences are meaningful, but no true zero (e.g., Temperature in °F — 0∘ doesn't mean "no heat").

Ratio

Ordered numbers with a true zero where ratios make sense (e.g., Price, distance, age — $0 means free, $10 is double $5).