A test consists of 910 true or false questions. If the student guesses on each question, what is the standard deviation of the number of correct answers?

$\setminus \sigma = \setminus \sqrt{n p \left(1 - p\right)}$
$= \setminus \sqrt{910 \cdot \left(0.5\right) \left(1 - 0.5\right)} \setminus \setminus = \setminus \sqrt{227.5} \setminus \approx 15.083103 \setminus \approx 15.083$