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

Multiple Choice

A consumer advocacy group tested the "on-air" lifetimes a random sample of 241 cell phone batteries. The mean lifetime was 3.2 hours with a standard deviation of 0.1 hours.
The lifetimes are approximately bell-shaped. Estimate the number of batteries with
Lifetimes between 3.0 hours and 3.4 hours.

A) almost all (greater than 229)
B) 164
C) 12
D) 229