- A statistic which measures the centre of a set of data by finding that value which divides the data in half. A technical definition is that the median is the value which is greater than or equal to half of the values in the data set and less than or equal to half the values. To compute the median yourself, you would sort the data from smallest to largest and then:
- for an odd number of observations, pick the centre value.
- for an even number of observations, pick the value halfway between the centre two.
- For a symmetric distribution such as the normal distribution, the median is the same as the mean.
- For a distribution which is skewed to the right, the median is typically smaller than the mean.
- For a distribution which is skewed to the left, the median is typically larger than the mean.
The median can be estimated from a histogram by finding the smallest number such that the area under the histogram to the left of that number is 50%.