Question

Refer to the accompanying technology display. The probabilities were obtained by entering the values of n equals 5 and p equals 0.764. In a clinical test of a​ drug, 76.4​% of the subjects treated with 10 mg of the drug experienced headaches. In each​ case, assume that 5 subjects are randomly selected and treated with 10 mg of the drug. Find the probability that at least four of the subjects experience headaches. Is it unusual to have fewer than four subjects experience​ headaches? Binomial with n equals 5 and p equals 0.764 x ​P(Xequals​x) 0 0.0007 1 0.0118 2 0.0767 3 0.2484 4 0.4020 5 0.2603

Answer 1

The the number of subjects X out of 5 who experiences headache has follows Binomial distribution with
The PMF of X is .

The probability that at least four of the subjects experience headaches is

The probability that fewer than four subjects experience​ headaches

Since the probability is approximately 34%, it is not unusual  to have fewer than four subjects experience​ headaches.