SOLUTION: In a certain high-risk group, the chance of a person having suffered a heart attack is 70%. If four persons are chosen from the group, find the probability that at least one will

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Question 464956: In a certain high-risk group, the chance of a person having suffered a heart attack is 70%. If four persons are chosen from the group, find the probability that at least one will have had a heart attack.
Found 2 solutions by ewatrrr, edjones:
Answer by ewatrrr(24785) About Me  (Show Source):
You can put this solution on YOUR website!
 

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 p= .70 and q = .30

nCx = n%21%2F%28x%21%28n-x%29%21%29

P(at least one in four) = 1 - P(none)

                              P(none) = .30^4

P(at least one in four) = 1 - .30^4 = .9919

Answer by edjones(8007) About Me  (Show Source):
You can put this solution on YOUR website!
1-.7=.3
.3^4=.0081 prob that none have a heart attack.
1-.0081=.9919 the probability that at least one will have had a heart attack.
.
Ed