Question 1115816: f the life, in months, of a certain type of car battery is normally distributed with a mean of 88months and a standard deviation of 9 months, what should be the guarantee period if the companywants less than 5% of the batteries to fail while under warranty?
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! 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
-----
Find the corresponding months::
x = -1.645*9+88
-----
x = 73.2
----
Ans:: Warranty for 73 months
--------------
Cheers,
Stan H.
----------
|
|
|
