What is a median?

The median is the value so that roughly half of the data are smaller and roughly half of the data are larger. There are two formulas for the computation of the median, depending on whether the size of your sample is even or odd. In both cases, sort the data. If n (the number of observations in your sample) is odd, select (n+1)/2 observation. If n is even, select halfway between the n/2 and n/2+1 observation.

• In a sample of adults, the LDL values are (in order from low to high): 1.84, 2.96, 3.49, 3.68, 3.72, 3.73, 3.84, 3.84, 4.14, 4.41, 4.80, 4.26, 5.57, and 5.85. For this data there are an even number of observations (n=14). So we would select halfway between the 7th observation (3.84) and the 8th observation (also 3.84). Thus the median is 3.84 for this data set.

This webpage was written by Steve Simon on 2002-10-11, edited by Steve Simon, and was last modified on 2008-07-08. This page needs minor revisions. Category: Definitions, Category: Descriptive statistics.