If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

# Mean and standard deviation of a binomial random variable

AP.STATS: UNC‑3 (EU), UNC‑3.C (LO), UNC‑3.C.1 (EK)
You might need: Calculator

## Problem

Ms. Davis is doing an activity with her statistics students where she gives them a 20-question multiple choice test, and they know none of the answers. Students need to guess on every question, and each question has 5 possible choices, 1 of which is correct.
What are the mean and standard deviation of the number of questions that each student gets correct?