median M is the midpoint of a distribution, the number such that half the observations are smaller and the other half are larger. To find the median:
1) arrange all the observations in order of size, from smallest to largest
2) if the number of observations is odd, the median M is the center observation of the order list.
3) if the number of observations is even, the median M is the mean of the 2 center observations in the ordered list.