# Standard deviation of a Bernoulli distribution?

Example:

We have a population of 100 people, where only 60 of them love pizza.

So, the probability of success is 0.6

SD[x] = $\sqrt{pq} = \sqrt{0.6 \times 0.4} = 0.48$

The definition of SD is :

"Standard Deviation (SD) is the measure of spread of the numbers in a set of data from its mean value."

"What does the value of the standard deviation (0.48) tell us?"

What kind of spread are we talking about in this pizza example ?

Obviously, if 99% of the people in your population like pizza, then you expect a '1' most of the time, so the variability in the result will be lower ($\sigma=\sqrt{0.01 \times 0.99}=0.0995$).
This variability will be largest when $p=0.5$.