SOLUTION: A test consists of 10 true-or-false questions. An answer is randomly chosen for each question. What is the probability of answering exactly 4 questions correctly?
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Question 368494: A test consists of 10 true-or-false questions. An answer is randomly chosen for each question. What is the probability of answering exactly 4 questions correctly? Found 2 solutions by Fombitz, ewatrrr:Answer by Fombitz(32388) (Show Source):
Hi,
Note: The probability of x successes in n trials is:
.
P = nCx* where p and q are the probabilities of success and failure respectively.
In this case both p & q are = 1/2 or .5
nCx =
A test consists of 10 true-or-false questions
P (exactly 4 correctly)= 210*(.5)^4 (.5)^6 = .205