StATS: 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 page was written by Steve Simon while working at Children's Mercy Hospital. Although I do not hold the copyright for this material, I am reproducing it here as a service, as it is no longer available on the Children's Mercy Hospital website. Need more information? I have a page with general help resources. You can also browse for pages similar to this one at Category: Definitions, Category: Descriptive statistics.