This is a question about the binomial distribution. Here the number of correct answers has distribution , where [tex]n=50[/math[ the number of Bernouli trials, and the probability of a favourable outcome on an individual trial.

Facts you should know about the binomial distribution:

Mean (or expected) number of favourable outcomes:

Variance of the number of favourable outcomes:

and so the standard deviation:

.

So in this case we have:

.

RonL