Mean, Median and Mode

The mean is the average of the numbers. It is easy to calculate: add up all the numbers, then divide by how many numbers there are.

http://www.kidsmathgamesonline.com/numbers/meanmedianmode.html

The mode is the value that occurs most often. If there is not a number that is repeated, then there is no mode for the list.

http://www.technologyrocksseriously.com/2011/04/mean-median-mode-range.html#.VaWypaaJeQE

The median is the middle value in the list of numbers. To find the median, your numbers have to be listed in numerical order. You may have to rewrite your list first to find the median.

http://www.quia.com/rr/51667.html