The variance is a measure of variability, and is often denoted by s2. In simple statistical methods the square root of the variance, s, which is called the standard deviation, is often used more. The standard deviation has the same units as the data themselves and is therefore easier to interpret. The variance becomes more useful in its own right when the contribution of different sources of variation are being assessed. This leads to a presentation called the “analysis of variance”, often written as ANOVA.