Median (mathematics).

Median (mathematics). Median (mathematics), the value of the middle member of a set of numbers when they are arranged in order. Like the mean (or average) and mode of a set of numbers, the median can be used to get an idea of the distribution or spread of values within a set when examining every value individually would be overwhelming or tedious. The median of the set {1, 3, 7, 8, 9}, for example, is 7, because 7 is the member of the set that has an equal number of members on each side of it when the members are arranged from lowest to highest. If a set contains an even number of values, there is no single middle member. In such cases the median is the mean of the two values closest to the middle. The median of the set {1, 3, 9, 10}, for example, is (3 + 9)/2 = 6. The mean is a more precise measure than the median, but can be greatly affected by a few numbers that are very different from the other members of a set. For example, the mean of the set {2, 4, 5, 7, 8, 934}--calculated by adding the members of the set together and dividing the sum by the total number of members--is 160, which is much higher than all but one of the values in the set. In cases such as this the median, 6, is used to give a better overall impression of the typical values of the numbers because it ignores outlying values. Microsoft ® Encarta ® 2009. © 1993-2008 Microsoft Corporation. All rights reserved.