Median

In probability theory and statistics, a median is a number dividing the higher half of a sample, a population, or a probability distribution from the lower half. To find the median of a finite list of numbers, arrange all the observations from the lowest value to the highest value and pick the middle one. If there is an even number of observations, one often takes the mean of the two middle values. There may be more than one median: for example if there is an even number of cases then there is no unique middle value. However, at least half the numbers in the list are less than or equal to either of the two middle values, and at least half are greater than or equal to either of the two values, and the same is true of any number between the two middle values. Thus, either of the two middle values and all numbers between them are medians in that case. When the median is used as a location parameter in descriptive statistics, there are several choices for a measure of variability: the range, the interquartile range, and the absolute deviation. The median is the same as the second quartile. To obtain the median of an even number of numbers, find the average of the two middle terms.