Question

A multiple choice test is given, in which each question has 5 possible answers. As part of an experiment in how students approach test-taking, the probabilities for getting answers correct just by guessing are calculated. If the test has 20 questions, what is the probability of getting 4 questions correct

Answer 1

Solution

Given that ,

p = 0.2

Using binomial probability formula ,

P(X = x) = (_n C _x) * p^x * (1 - p)^{n - x}

P(X = 4) = (₂₀ C ₄) * 0.2⁴ * (0.8)¹⁶

Probability = 0.0349

.