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

question 49

Multiple Choice

A consumer advocacy group tested the "on-air" lifetimes of a random sample of 152 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 2.5 hours and 3.3 hours.

• A) 103
• B) 144
• C) almost all (greater than 144)
• D) 49

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