This tutorial will discuss interval and ratio levels of measurement by focusing on:
An interval measurement is based on an arbitrary scale. The value of zero doesn't necessarily mean that it's the bottom. An example of this would be temperature, where you can have negative temperatures. However, the intervals are still useful in that differences can be compared directly.
Celsius scale of temperature. You may not know this, but the coldest that anything can get, the point at which atoms in a molecule cease to move, is negative 273 degrees Celsius.That's called absolute zero. Notice that it is not where zero degrees Celsius is. Zero degrees Celsius is the freezing point of water. So the fact that zero placed zero where it is on the line is fairly arbitrary.
When you look at values other than zero, like 50 and 100 degrees, you may tempted to say that 100 degrees is twice as hot as 50 degrees, when in fact, that's not really the case. If you look at the absolute zero temperature,100 is only a little bit further out than 50. It's not twice as far out as 50, so it's not twice as hot.
However, remember what we said before. The intervals are still useful in that you can compare differences. Meaning, the difference between 50 and 100 is the same as the difference between 0 and 50.
So you can compare the differences, you just can't compare the values themselves.
By contrast, ratio measurements can compare in terms of relative distance from 0. In the case of temperature, you can measure values themselves but only if you measure from absolute zero.
Other examples of ratio levels include mass. Something that has a mass of 20 grams is twice as massive as something that has a mass of 10 grams. And when we thing of length, something that's 20 meters long is twice as long as something that's 10 meters long.
With ratio measurements, the measurement of zero is fixed, and so the values can be compared in terms of how far they are from zero. However, interval measurements are based on an arbitrary scale and the values cannot be compared. You can use the terms double, or half, or a third, or three times as far. And so the terms we used in this tutorial are interval measurements and ratio measurements.
Source: This work is adapted from Sophia author jonathan osters.