Question

A grocery bag can be classified as either paper or plastic . Suppose that 92 ​% of grocery bags are classified as plastic . ​(a) Two grocery bags are chosen at random. What is the probability that both grocery bags are plastic ​? ​(b) Nine grocery bags are chosen at random. What is the probability that all nine grocery bags are plastic ​? ​(c) What is the probability that at least one of nine randomly selected grocery bags is paper ​? Would it be unusual that at least one of nine randomly selected grocery bags is paper ​?

Answer 1

p = 0.92

a) P(both bags are plastic) = 0.92² = 0.8464

b) P(all nine bags are plastic) = 0.92⁹ = 0.4722

c) P(at least one out of 9 bags is paper) = 1 - P(zero bags are paper)

                                                                = 1 - P(all nine bags are plastic)

                                                                = 1 - 0.4722

                                                                = 0.5278

No this is not unusual, because the probaility is not less than 0.05