A multiple choice test consists of eight questions, each of which has five choices. Each question has exactly one correct answer.

William guesses randomly at each answer. What is the probability that he gets six or fewer questions correct?

Question

A multiple choice test consists of eight questions, each of which has five choices. Each question has exactly one correct answer.

William guesses randomly at each answer. What is the probability that he gets six or fewer questions correct?

ganeshie8 · Answer

$\large P(X\le 6) =   1 - [P(7) + P(8)] $

ganeshie8 · Answer

its a binomial distribution, u knw how to find P(7) and P(8) ?

ganeshie8 · Answer

$P(7) =  ~^8C_7  (\frac{1}{5})^7(\frac{4}{5})$

$P(8) = (\frac{1}{5})^8$

ganeshie8 · Answer

evaluate and plugin