A median is the middle number in an ordered numerical sequence. If there are two middle numbers (i.e. there is an even number of terms in the sequence), then the median is found by taking the mean of the two middle numbers.
So in an example of the following numerical values:
- 2, 4, 5, 11, 13
The median is 5, as there are 2 values less than 5 and 2 values greater than 5.
The median is sometimes preferred as a measure of centrality over the mean due to the fact that is isn't as affected by outliers as the mean is.