# Statistics for Modern Life: 03 Ratio Scales

By Robert Ramstetter, 27th May 2015 | Follow this author
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A Scale that has a Definitive Starting Point of Zero. This is one of the key building blocks of understanding Statistical formulas.

## Ratio Scales have a Starting Point of Zero

What Is a ratio scale? You will see this used extensively in Statistics. Simply put, a ratio scale must have a true starting point of zero so that a true ratio can be measured. Suppose, for instance, you were to compare the high temperature over two days. On the first day, the high temperature was 10 degrees celsius. The high temperature on the second day was 20 degrees celsius. Would it be fair to say that the second day was twice as warm as the first?

At first glance, you might think that, since 20 is twice as much as 10, that the second day is twice as warm as the first. That statement would be incorrect, though. The problem lies with the fact that, whether you are measuring temperature with Celsius or Fahrenheit, zero degrees is an arbitrary number. Zero degrees Celsius is the point at which water freezes, whereas zero degrees Fahrenheit is the point at which sea water freezes. They are simply a point at which zero was determined by someone for some reason.

For the scientists who read this, the Kelvin temperature scale begins at absolute zero. That is the point at which all molecular activity ceases and nothing can get colder. Therefore, on the Kelvin temperature scale, with an absolute starting point of zero, it is correct to state that, on a ratio scale, 20 degrees is twice as warm as 10 degrees. There is twice as much molecular activity and, therefore, twice as much heat.

If you were to compare the distance that two objects traveled, you would be correct in applying a ratio scale to it. For instance, one car travels 15 kilometers and another travels 45 kilometers. Since they both had the starting point of zero kilometers, you could say that the second car traveled three times as far as the first. That would be an example of applying a ratio scale to the results.

Understanding the concept of a ratio scale is absolutely necessary to understand Statistics. It is one of many scales that you will use. An incorrect understanding of the ratio scale concept will result in incorrect statistical data.

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