A cell phone company says that a fully charged battery lasts 14 hours. In reality, each battery behaves a little differently. For a large quantity of fully charged batteries, the mean length of time that batteries last is 14 hours, with a standard deviation of 1 hour. Assume that the lengths of time that battery charges last can be modeled by a normal distribution.

What percentage of fully charged cell phone batteries whould be expected to last between 12 and 14 hours?

What percentage of fully charged cell phone batteries whould be expected to last less than 15 hours?

Would it be surprising if a fully charged cell phone battery lasted more than 17 hours? Explain why it why not.


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