Degrees of Freedom

Description

To explain degrees of freedom, let's look at an example. In a set of three numbers, the mean is 10, and two out of three variables are five and 15. This means there's only one possibility for the third value: 10. With any set of three numbers with the same mean, for example, 12, eight, and 10 or say nine, 10, and 11, there's only one value for any two given values in the set. Essentially, you can change the two values and the third value fixes itself. The degree of freedom here is two.

In other words, degrees of freedom is the number of independent data points that went into calculating the estimate. As we see in the example above, it is not necessarily equal to the number of items in the sample (n).