SupremeCookie said: I'm going to ask you a second time. What do you know about standard deviation? What does it tell you? It's a matter of recalling the definition. I wish that you would put the same effort into trying to answer my question, rather than spending your time writing the rubbish responses. I can say that with absolute certainty, i.e. a standard deviation of 0, that is the wisest way to spend your time. Click to expand... The standard deviation is a way to measure the variation. For example, suppose we have a set of values of that variation. The higher the standard deviation, the further will be these values are spread out from the mean. To understand the idea visually, imagine that you have a standard normal distribution where the mean, zero, divides the distribution area equally. Now approximately 34.1% of the area will lie within a width equal to 1 standard deviation from one side of the mean.