Definition
Average of absolute differences (differences expressed without plus or minus sign) between each value in a set of values, and the average of all values of that set. For example, the average (arithmetic mean or mean) of the set of values 1, 2, 3, 4, and 5 is (15 ÷ 5) or 3. The difference between this average (3) and the values in the set is 2, 1, 0, 1, and 2; the absolute difference being 2, 1, 0, 1, and 2. The average of these numbers (6 ÷ 5) is 1.2 which is the mean deviation. Also called mean absolute deviation, it is used as a measure of dispersion where the number of values or quantities is small, otherwise standard deviation is used.
Use mean deviation in a sentence

As part of her statistics project, Caitlin had to calculate the mean deviation of her data set but because she had so many values, she could not do it by hand and had to use a calculator.

You should try to figure out how to break down the mean deviation and use that info to create new plans.

I had to find out the mean deviation, which would be pretty hard and would take me a long time to do.
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