Question 14994
A certain drug has an 80% success rate in relieving the symptoms of migraine.
In a group of 12 patients what is the probability that;
6 are helped by the drug
At least i is helped by the drug
No more than 2 are still suffering the effects of migraine 
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These are all binomial because people are either helped or are not helped.
In a group of 12 patients what is the probability that;
6 are helped by the drug
n=12 ; p=0.80 ; x=6
Using a TI calculator use binompdf(12,0.8,6) to get 0.055
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At least ? is helped by the drug
Use [1-binomcdf(12,0.8,?-1)]
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No more than 2 are still suffering the effects of migraine 
Use binomcdf(12,0.8,2)=4.526 x 10^-6 = 0.000004526
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If you don't have a TI or are allowed to use a calculator
let me know.
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Cheers,
Stan H