Understanding Basic Statistics 6th Edition by Charles Henry Brase,Corrinne Pellillo Brase

Exercise 160

Health: Lead Contamination More than a decade ago, high levels of lead in the blood put 88% of children at risk. A concerted effort was made to remove lead from the environment. Now, according to the Third National Health and Nutrition Examination Survey ( NHANES III ) conducted by the Centers for Disease Control and Prevention, only 9% of children in the United States are at risk of high blood-lead levels.
(a) In a random sample of 200 children taken more than a decade ago, what is the probability that 50 or more had high blood-lead levels
(b) In a random sample of 200 children taken now, what is the probability that 50 or more have high blood-lead levels