I vaguely recall a "shortcut" sort of formula for calculating the standard deviation for a population. For example, if theres a yes/no survey and 53% of 1,000 people votes yes, what's the standard deviation from the expectation?

I recall such a formula from my Stats 1 class years ago. It was something like:

(Number voting yes / Total votes) + (Number voting no / Number votes) * sqrt(something)