Asked by poe

A test is composed of six multiple choice questions where each question has 4 choices. If the answer choices for each question are equally likely, find the probability of answering 3 OR 4 questions correctly.
Answered by Writeacher
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Answered by Reiny
R --- right
W --- wrong

so we want the case of
RRRWWW or RRRRWW and its possible arrangements

P(3 R) = C(6,3)(1/4^3(3/4)^3 = .131836
P(4 R) = C(6,4)(1/4)^4(3/4)^2 = .032959

P(3R or 4R) = the sum of those two
= .1648
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