Multiple Choice Test: Binomial Probability
Date: 08/05/97 at 18:55:12
From: Heather
Subject: Multiple choice test
A multiple choice test consists of 9 questions with 5 choices for each
answer. If a student guesses randomly, find the probability of each of
the following events:
1. The student gets 5 correct
2. The student gets at least 5 correct
3. The student gets 2 correct answers
4. The student gets fewer than 3 correct answers.
Date: 08/06/97 at 11:55:26
From: Doctor Anthony
Subject: Re: Multiple choice test
This is binomial probability with n = 9, p = 1/5, q = 4/5
1. P(5) = 9C5 (1/5)^5 (4/5)^4 = 0.016515
2. At least 5 is = P(5) + P(6) + P(7) + P(8) + P(9)
P(6) = 9C6 (1/5)^6 (4/5)^3 = .0027525 and so on.....
3. P(2) = 9C2 (1/5)^2 (4/5)^7 = 0.301989
4. P(< 2) = P(0) + P(1)
P(0) = (4/5)^9 = 0.1342177
P(1) = 9C1 (1/5) (4/5)^8 = 0.301989
So P(<2) = Sum of these = 0.43621
Doctor Anthony, The Math Forum
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