SOLUTION: find the probability that exactly 5 of the 12 companies test for substance abuse How do i find the probability that at least half of the companies test for substance abuse? 8

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Question 470656: find the probability that exactly 5 of the 12 companies test for substance abuse
How do i find the probability that at least half of the companies test for substance abuse?
80% test employees for substance abuse, the study involves the random selection of 12 companies
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(CO test) = .8  & q = .2

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

P(exactly 5 test) = 12C5(.8)^5(.2)^7 = 792(.8)^5(.2)^7 = .0033

P(at least half) = 1 - P(0)-P(1)-P(2)-P(3)-P(4)-P(5)= .9961

Recommend the use of a personal statistical calculator or using the calculators on sites such as: stattrek.com