Which of the following is an example of an interval data scale?

• A. Color categories
• B. Weight
• C. Temperature in Celsius
• D. Customer satisfaction rating

Answer: (C)

Interval data scales have equal, meaningful differences between values but do not have a true zero that represents the absence of the quantity. Temperature on the Celsius scale fits this: the difference between 20°C and 21°C is the same increment as between 0°C and 1°C, so differences and averages are meaningful. However, zero on the Celsius scale does not mean there is no temperature, so you can’t say one temperature is twice another. In contrast, weight is a ratio scale because zero weight means none and you can meaningfully say one weight is twice another. Color categories are nominal, and customer satisfaction ratings are ordinal, so they don’t meet the criteria for interval data.