Posted by please help me! on Tuesday, March 23, 2010 at 2:21pm.
prob of R(ight) = 4/20 = 1/5
prob of W(rong) = 4/5
1) to have exactly 9R and 11W
= C(20,9)((1/5)^9(4/5)^11
= ....
( I got .00722)
2) to get the prob of less than 9 you will have to do
prob(0R) + prob(1R) + prob(2R) + .. + prob(8R)
I will do prob(R4)
= C(20,4)(1/4)^4(4/5)^16 = .21819
Follow the same pattern for the other calculations
a test consists of 25 multiple choice questions. Each has 5 possible answers, which only one is correct. If a student guesses on each question, find the following:
a) prob that he will guess all of them right
b)prob that he will guess at most 12 right
c) prob that he will guess at least 1 right
d) mean and stndrd. deviation of the number of correct answers
e)estimate the prob of the number of correct answers that will fall within the limits -----> miu +or- 2(stand.dev)
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