Question

The Bank of america trends in Consumer Mobility Report indicates that in a typical day, 51% of users of mobile phones use their phone at least once per hour, 26% use their phone a few times per day, 8% use their phone morning and evening, and 13% hardly ever use their phones. The remaining 2% indicated that they did not know how often they used their mobile phone (USa today, July 7, 2014). Consider a sample of 150 mobile phone users. A. What is the probability that at least 70 use their phone at least once per hour? B. What is the probability that at least 75 but less than 80 use their phone at least once per hour? C. What is the probability that less than 5 of the 150 phone users do not know how often they use their phone?

Answer 1

Solution and Explanation:

a)  51% of users of mobile phones use their phone at least once per hour,

It is a binomial distribution with n = 150, p = 0.51

mean = np = 150 multiply with 0.51 = 76.5

SD= sqrt(np(1-p) )= 6.1225

Since np and n(1-p) > 5, we can assume the distribution is normal.

B) please see the attached file.

c)  It is a binomial distribution with n = 150, p = 0.02

mean = np = 150*0.02 = 3

SD= sqrt(np(1-p) )= 1.71464

Since np < 5, we cannot assume the distribution is normal.