Question

Is the following classified as interval, ordinal or nominal data?

The marks achieved by the students in a statistics course out of 100.

Answer 1

One would hope the grades are interval.

Answer 2

Hoping isn't enough.

The intervals are not necessarily equal. In other words, the difference between 10-40 would not necessarily mean the same as the difference between 60-100. The scale is only ordinal. All you can say for sure is that a higher score indicates greater knowledge of statistics, and a lower score indicates less.

I. Nominal scale names or classifies only (social security number, baseball, football examples).

II. Ordinal scale — also ranks beside naming (height, baseball standings, beauty pageant examples). Most tests are only ordinal scales.

III. Interval scale — beside previous qualities, also has equal intervals and an arbitrary zero (centigrade/Fahrenheit thermometer examples).

IV. Ratio scale also has a true/absolute zero, which allows comparisons in terms of ratios (Kelvin thermometer, height/weight measurements). Math uses ratio scale.

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