Question 230428: In testing a new drug, researchers found that 20% of all patients using it will have a mild side effect. A random sample of 15 patients using the drug is selected. Find the probability that:
(a) exactly four will have this mild side effect.
(b) at least seven will have this mild side effect.
I understand how to do a, and I go the answer of .188, but I don't know how to do the setup for b. I used the formula to calculate binomial probabilities for a, what do I do for be. I'm not looking for an answer, I would just like the setup explained on how to get the answer. Thanks for your help.
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! In testing a new drug, researchers found that 20% of all patients using it will have a mild side effect. A random sample of 15 patients using the drug is selected. Find the probability that:
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Binomial with n=15, p=0.2
(a) exactly four will have this mild side effect.
P(x=4) = 15C4(0.2)^4(0.8)^11) = 0.1876...
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(b) at least seven will have this mild side effect.
I understand how to do a, and I got the answer of .188, but I don't know how to do the setup for b.
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You could add up P(x=7)+P(x=8)+....+P(x=15)
OR
You should have a binomial table in your text (or find one online)
that will give you the p(0<= x <=6). Subtract that number from 1
and you will have P(7 <= x <= 15)
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I get 0.0186..
Cheers,
Stan H.
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