6.13 Why the difference?
Refer to the previous exercise. In Exercise 6.1 (page 289), a survey by AppsFire reported a median of 108 apps per device. This is very different from the average reported in the previous exercise.
6.13
(a) In 6.1, the population was all AppsFire users, while in 6.12, the population is all U.S. smartphone subscribers. It is likely that one group has more apps. (b) Excluding those with no apps will increase the mean/median and could account for the difference.