Question 185999: This is a college stats problem-
In testing a new drug, researchers found that 5% of all patients using it will have a mild side effect. A random sample of 11 patients using the drug is selected. Find the probability that:
a) exactly 2 will have this mild side effect
I can't figure this part out- 11/9*2???
b) at least 1 will have this mild side effect
1 - (0.95^11) = 0.4312
Thanks
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! In testing a new drug, researchers found that 5% of all patients using it will have a mild side effect. A random sample of 11 patients using the drug is selected. Find the probability that:
a) exactly 2 will have this mild side effect
Ans: binompdf(11,0.05,2) = 0.0867
Another way to get that answer P(x=2) = 11C2(0.5)^2*(0.95)^9 = 55*0.0025*0.6302
= 0.0867
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b) at least 1 will have this mild side effect
Ans: 1 - binompdf(11,0.05,0) = 0.4312
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Another way: P(1<=x<=11) = 1-P(x=0) = 1- 11C0(0.05)^0(0.95)^11
= 1 - 1*1*0.95^11 = 1-5688= 0.4312
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You must let me know if you do not understand these answers.
It is essential that you understand how to calculate binomial
probabilities.
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Cheers,
Stan H.
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