4
(Choose1answer)
Assume that number of apps used per month by smartphone owners is normally distributed with an average of 20 apps per month and the standard deviation is 3. If you select a random sample of 30 smartphone owners,what is the probability that the sample mean is between 18 and 22?
Let P(Z < -3.65) = 0.00013; P(Z < 3.65) = 0.99987; P(Z-2) = 0.0228; P(Z < 2)= 0.9772.
A. 0.00013
B. 0.99987
C. 0.99974
D. 0.97720
E. None of the other choices is correct
