A tire manufacturer states that a certain type of tire has a mean lifetime of 60,000 miles. Suppose lifetimes are normally distributed with standard deviation ơ = 3,500 miles.
Define the standard random variable Z as
Where X denotes lifetime
a) Using normal table we have
b) Required probability is
c) Let be the mileage such
that
Then we know from normal table that
Hence
So the mileage should be 64,480
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