Statistics for People Who (Think They) Hate Statistics

by Neil J. Salkind

The standard deviation is computed as the average distance from the mean. So, you will need to first compute the mean as a measure of central tendency. Don’t fool around with the median or the mode in trying to compute the standard deviation. The larger the standard deviation, the more spread out the values are, and the more different they are from one another. Just like the mean, the standard deviation is sensitive to extreme scores. When you are computing the standard deviation of a sample and you have extreme scores, note that fact somewhere in your written report and in your interpretation of what the data mean. If s = 0, there is absolutely no variability in the set of scores, and the scores are essentially identical in value. This will rarely happen and actually makes it hard to compute statistics about the relationship between scores. Without variability, we can’t see connections between variables. And, when you think about it, a variable is only a variable when it varies.