Ordinal vs. Interval Data: Key Differences Explained
Ordinal data sorts things into order—like small, medium, large—while interval data gives ordered numbers with equal gaps—like temperature in Celsius or test scores.
People mix them up because both involve numbers and ranking. A 5-star rating feels like a score, so it’s tempting to treat it like interval data. But the gap between 4 and 5 stars may not equal the gap between 2 and 3, making it ordinal.
Key Differences
Ordinal = rank without guaranteed equal steps. Interval = rank with equal steps but no true zero. Think of race places (ordinal) versus temperature (interval).
Which One Should You Choose?
Use ordinal for surveys, satisfaction, or any ranking where gaps aren’t equal. Use interval for temperature, IQ, or any scale where differences between points are meaningful and consistent.
Examples and Daily Life
Ordinal: movie ratings, medal colors. Interval: calendar years, SAT scores. Remember, the choice shapes how you interpret and report findings.
Is money interval or ordinal?
Money is ratio data—it has a true zero and equal intervals. Don’t label it ordinal or interval.
Can I average ordinal data?
Averaging isn’t recommended; use median or mode instead to stay true to its ranking nature.