Learn in the textbookData Operations and Levels of Measurement
DefinitionAn interval scale (間隔尺度) is a scale with equal intervals between its marks, so the difference between values has meaning, but 0 does not mean there is no quantity.
ExplanationTemperature in degrees Celsius and calendar years are examples. Because 0 ℃ is not a state with no temperature but simply the chosen starting point of the scale, 20 ℃ cannot be called twice as hot as 10 ℃. Addition, subtraction and averages are meaningful, but ratios (how many times larger) are not.
AnalogyIf everyone is measured while standing on the same platform of a height gauge, every reading is off by the platform's height, yet the difference between any two people stays the same. The scale keeps differences but not ratios.