A Consumer Advocacy Group Tested the "On-Air" Lifetimes of a Random

Multiple Choice

A consumer advocacy group tested the "on-air" lifetimes of a random sample of 162 cell phone batteries. The mean lifetime was 2.9 hours with a standard deviation of 0.4 hours. The lifetimes are approximately bell-shaped. Estimate the number of batteries with lifetimes between 2.1 hours and 3.7 hours.

A) 110
B) 8
C) almost all (greater than 154)
D) 154