Question

If there are 19 questions and each question has 4 answers, what is the probability she will answer at least one question correctly?

Answer 1

0.9958

Explanation:

P(being correct) = 1/4 = 0.25

Hence, p = 0.25

n = 19

P(x ≥ 1) = p(x = 1) + p(x = 2) +... + p(x = 19)

Using the binomial probability formula :

P(x =x) = nCx * p^x * (1 - p)^(n - x)

However, to save computation time, we could use a calculator :

Using a calculator,

P(x ≥ 1) = 0.99577

P(x ≥ 1) = 0.9958