A survey shows that 45% of the respondents pick option A. Given that 50 people replied, what is the standard error of the proportion

The formula for the standard error is this:

σM = σ / √N

where

σM is the standard error

σ is the standard deviation

N is the number of samples

So,

σM = 0.45 / √50

σM = 0.0636 or 6.36%

The standard error is 0.0636