• Standard Deviation is a measure of dispersion around the mean (statistical average). For example, if half the class weighed 200 lbs and the other half weighed 100 lbs, the mean (or average) would be 150 lbs.
• There would be a large standard deviation if this were the case.
• If everyone but two people in the class weighed 150 lbs, and one person weighed 145 and the other 155, the mean would still be 150 lbs, but the standard deviation would be closer to zero.

For more information about means, standard deviations, etc. Click the link below: http://nilesonline.com/stats/stdev.shtml