Reference table
The four levels of measurement in survey data
Nominal, ordinal, interval and ratio, and the statistics each one allows
A reference table of Stevens' four levels of measurement as they apply to survey and interview data. For each level it shows what the numbers carry, which relabelling of the scale changes nothing, which summaries stay meaningful and a familiar research example. Use it while planning a survey, so the questions you ask produce the level your report needs. Koji maps each structured question type to a level and reports summaries to match.
Where this appears
What's in this reference table
| Level | What the numbers encode | Harmless relabelling | Summaries that survive | Research example |
|---|---|---|---|---|
| Nominal | Identity only | Any one-to-one swap of labels | Counts, percentages, mode, chi-square | Plan tier, region, the theme a quote was coded to |
| Ordinal | Order | Any order-preserving change | All of the above plus median, percentiles, top-box share, rank correlations | Satisfaction rating, a ranking, company size bands |
| Interval | Order and equal spacing | Multiply by a positive number and add a constant | All of the above plus mean, standard deviation, Pearson correlation | Temperature in Celsius, rating scales by convention |
| Ratio | Order, equal spacing and a true zero | Multiply by a positive number | All of the above plus ratios, percent change, coefficient of variation | Sessions per week, minutes to complete a task, spend |
Use this image
Free to use in your docs, decks and posts under CC BY 4.0, as long as you credit Koji with a link to this page. To embed it, paste this into your page:
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<a href="https://www.koji.so/visuals/levels-of-measurement-nominal-ordinal-interval-ratio"><img src="https://www.koji.so/visuals/levels-of-measurement-nominal-ordinal-interval-ratio/levels-of-measurement-nominal-ordinal-interval-ratio.png" alt="Table of the four levels of measurement, nominal, ordinal, interval and ratio, with the summaries each allows and a research example of each." width="1200" height="914" /></a>
<p>Source: <a href="https://www.koji.so/visuals/levels-of-measurement-nominal-ordinal-interval-ratio">The four levels of measurement in survey data</a>, Koji</p>
