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## Statistics and probability

### Course: Statistics and probability>Unit 3

Lesson 4: Variance and standard deviation of a population

# The idea of spread and standard deviation

See how distributions that are more spread out have a greater standard deviation.

## Introduction to standard deviation

Standard deviation measures the spread of a data distribution. The more spread out a data distribution is, the greater its standard deviation.
For example, the blue distribution on bottom has a greater standard deviation (SD) than the green distribution on top:
Interestingly, standard deviation cannot be negative. A standard deviation close to $0$ indicates that the data points tend to be close to the mean (shown by the dotted line). The further the data points are from the mean, the greater the standard deviation.

## Try it yourself

Which of the data distributions shown below has the greater standard deviation?