How do you find the outlier in the data: 32, 40, 34, 3 l, 20, 36, 40, 31?

The outlier in this data is 20.

To find the outlier, you must find the number that is the most different from the others. In this case, 20 only appears once, and it is farther from the other numbers. For example, 31 and 34 are only 3 numbers away from each other, 40 and 36 are four numbers away from each other. 20 is eleven numbers away from the closest number, which is quite a bit farther than is the case with any other number in this data, thus making 20 the outlier.