Question 974111
 USA Today reports that about 25% of all prison parolees become repeat offenders. Alice is a social worker whose job is to counsel people on parole. Let us say success means a person does not become a repeat offender. Alice has been given a group of four parolees.
(a) Find the probability P(r) of r successes ranging from 0 to 4. (Round your answers to three decimal places.)
P(0) = 4C0*(0.75)^0*0.25^4
P(1) = 4C1*(0.75)*0.25^3
P(2) = 4C2*(0.75)^2 * 0.25^2
P(3) = etc.
P(4) = etc.

(c) What is the expected number of parolees in Alice's group who will not be repeat offenders? (Round your answer to two decimal places.)
Ans: mean = np = 4*0.75 = 3
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What is the standard deviation? (Round your answer to two decimal places.)
Ans: std = sqrt[npq] = sqrt[3*0.25] = (1/2)sqrt(3)
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(d) How large a group should Alice counsel to be about 98% sure that three or more parolees will not become repeat offenders?
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Cheers,
Stan H.
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