The answer is the mean. In statistics, the standard deviation is a measure that is used to compute the amount of variation or distribution of a set of data values. In other words, standard deviation (also variance) are measures of the spread of the data around the mean. They summarize how near each observed data value is to the mean value. A low standard deviation indicates that the data points tend to be close to the mean (otherwise known as the expected value) of the set, while a high standard deviation indicates that the data points are vast over a wider range of values.