Standard Deviation

The standard deviation is how far away each observation is, on average, from the mean of the data. We use standard deviation as a measure of spread about the mean, just as we use the interquartile range as a measure of spread about the median. Standard deviation, as paired with the mean, is typically used in symmetric or roughly symmetric data sets.

We can calculate the standard deviation using a long formula, or we can simply find it in the calculator when we do a 5-number summary (1-var statistics). Don't forget to always interpret it in the context of the problem!