<PRE><B>Question 1115816</B>
 If the life, in months, of a certain type of car battery is normally distributed with a mean of 88 months and a standard deviation of 9 months, what should be the guarantee period if the company wants less than 5% of the batteries to fail while under warranty? 
Find the z-value with a left tail of 5%.
invNorm(0.05) = -1.645
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Find the corresponding months::
x = -1.645*9+88
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x = 73.2
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Ans:: Warranty for 73 months
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Cheers,
Stan H.
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