Question 322383
A vaccine is 80% effective in preventing Type B influenza. In other words, 80% of those receiving the vaccine will not catch this type of flu. 
A random sample of 100 people has been given the vaccine. What is the probability that at least 75 will not catch this type of flu?
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Binomial with n = 100 and p = 0.8
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P(75<= x <=100) = 1 - binomcdf(100,0.8,74) = 0.9125
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Cheers,
Stan H.