As mentioned earlier, standard deviation tells us how far numbers in a set are spread out from their mean. Let's compare two datasets, presented in two histograms below.

For the first histogram, the mean is equal to 0 and the standard deviation equals approximately 2.22. For the second histogram, the mean and the standard deviation are equal to 0 and approximately 4.73, respectively. Notice that while the means for these two datasets are the same, the standard deviations differ greatly. The data represented by the second histogram—with greater standard deviation—are spread farther from the mean, whereas the data from the first dataset are all clustered together near the mean.