# Solved – Standard deviation of a dichotomous variable

Suppose, I have a dichotomous variable – gender:

Male coded as 0 Female coded as 1

Frequency of male – 30 Frequency of female – 20

The mean of a dichotomous variable is just the proportion which has been coded as 1. So, in this case, I believe it is 30/50.

The confusing part is while solving for standard deviation. How can I do that? Also, is the answer a meaningful one?

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If you code males as 0 and females as 1, the mean will be $$frac{20}{50}$$, not $$frac{30}{50}$$.
For the SD, just use the standard formula with your coding, $$x_iin{0,1}$$ and the mean $$frac{20}{50}$$ you calculated above.