ABSTRACT
The mean, or average, of a set of values is the sum of the values divided by the number of values:
The median of a set of values is the middle item (or the mean of the two middle items) when the data is arranged in an increasing or decreasing order of magnitude. The median is not so much affected by extreme values
Given the mean of several sets of data, the overall mean can be computed if the number of elements in each data set is known:
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