# Measures of Spread – Interpreting Standard Deviation

Standard deviation of data gives a lot of information about data that is approximately bell-shaped. Adrian Gepp explains more in this video.

## Interpreting Standard Deviation

Standard deviation is an important measure of spread because of how it can be interpreted for data that is approximately bell-shaped. Specifically, it gives an indication of how much is how far away from the mean. If the data is approximately bell shaped then:

• 68% of the data is within plus or minus one standard deviation around the mean
• 95% of the data is within plus or minus two standard deviations around the mean
• 99.7% of the data is within plus or minus three standard deviations around the mean

This result means that standard deviation is a very descriptive statistic! Now that we have some tools for measuring spread, let’s look at how we measure shape in the next step.