SOLUTION: A student takes a 20-question, true/false exam and guesses on each question. fkind the probability of passing if the lowest passing grade is 15 correct out of 20. How do I comput
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Question 316540: A student takes a 20-question, true/false exam and guesses on each question. fkind the probability of passing if the lowest passing grade is 15 correct out of 20. How do I compute using the binomial distribution formula:
P(X) = n! *p
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(n-x)!X! Answer by solver91311(24713) (Show Source):
The basic formula for the probability of exactly successes out of trials where the probability of a successful outcome on a single trial is fixed at is given by:
Where is the number of combinations of things taken at a time and is calculated by:
But you need the probability of 15 right answers plus 16 right answers plus ... plus 19 right answers plus 20 right answers.
So you need:
But since , we can write:
Get busy. You have some serious calculator punching to do. Or you can use Excel. The formula: =COMBIN(N,K) where N and K are the values you want gives you the value of
I ran this out and got a little over 2% probability.
SUPER-DOOPER DOUBLE PLUS EXTRA CREDIT.
10 question multiple-choice exam. All questions have four possible responses. Passing grade is 6 or better correct. Probability you can pass by just guessing?
