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) About Me  (Show Source):
Answer by ewatrrr(24785) About Me  (Show Source):
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Hi,
Note: The probability of x successes in n trials is:
.
P = nCx* p%5Ex%2Aq%5E%28n-x%29 where p and q are the probabilities of success and failure respectively.
In this case both p & q are = 1/2 or .5
nCx = n%21%2F%28x%21%28n-x%21%29%29
A test consists of 10 true-or-false questions
P (exactly 4 correctly)= 210*(.5)^4 (.5)^6 = .205