The median is the middle value. In order to find this measure of central tendency, put all the readings in numerical order, from smallest to largest, or from largest to smallest. Then, find the value in the middle. For example, if you have collected readings of 12, 6, 5, 9, 11, 10, and 9, you would first put them in order as 12, 11, 10, 9, 9, 6, 5. The number in the middle is the 9, with three numbers to the left of it, and three to the right. So, the median value of this set of readings is 9.

If you have an even number of readings, you will have to calculate the number in the middle by finding the mean of those two numbers. Say you have these readings: 6, 5, 4, 2, 2, 1. The median occurs between the numbers 4 and 2. So, find the mean of these two numbers -- add the 4 and 2 to get 6, and then divide by 2 (the number of readings) to get 3. That value is the median for this particular set of data.