Suppose the probability of someone wearing a pair of glasses among 5th graders is 39.3%. If there are 52 kids in a class, what will be the standard

Suppose the probability of someone wearing a pair of glasses among 5th graders is 39.3%. If there are 52 kids in a class, what will be the standard deviation of this distribution?

Not sure how to get the standard deviation, but I think the variance should be: