Suppose that the probability that a person between the ages of 19 and 24 checks their daily horoscope is 0.12. If 400 randomly selected people between the ages of 19 and 24 were asked "Do you check your daily horoscope?", would you be surprised if 63 or more said yes to this question? Why?
A)Cannot be determined with the given information.
B)No, 63 is within the expected range of people.
C)Yes, 63 would be an unusually large number of people given the known probability of 0.12.
D)Yes, 63 would be an unusually small number of people given the known probability of 0.12.

Question

Quizplus · Accepted Answer

The expected number of people who check their horoscope is 400 * 0.12 = 48. The standard deviation is sqrt(400 * 0.12 * 0.88) ≈ 6.48. A count of 63 is more than 2 standard deviations above the mean (48 + 2*6.48 ≈ 60.96), making it unusually large.

Suppose That the Probability That a Person Between the Ages