the mean (or average) is all the data points that are collected added up then divided by the total number of points.

example. below are the data points collected: 3 5 6 9 17 20

step 1. add: 3+5+6+9+17+20 = 60 step 2. divide: 60/6 = 10

see how there are 6 numbers that add up to 60, those are the data points.

the median is the number right in the middle of all the data points when put in number order. the easy way is to take the outside numbers & start counting off on each side "1 ,2..." and so on until there's only the middle number left. if there's an even number of points then take the two middle points, add them together & divide them by 2.

example. below are the data points collected:
3 5 6 9 17 20

1 2 3 3 2 1

as you can see there's 2 middle numbers, so add them (6+9=15), and divide by 2 (15/2), so the median of this set should be 7.5