SOLUTION: The mean lifetime of a printer is 48 months, with a standard deviation of 7 months. If the distribution of the printer lifetime is normal, for how many months should a guarantee be

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Question 1174438: The mean lifetime of a printer is 48 months, with a standard deviation of 7 months. If the distribution of the printer lifetime is normal, for how many months should a guarantee be made if the manufacturer does not want to exchange more than 10% of the watches? Assume the variable is normally distributed. (Round up whatever you get for the number of months the guarantee should be given for.)
Answer by ewatrrr(24785)   (Show Source): You can put this solution on YOUR website!

Hi
  Normal Distribution:  μ = 48m  and   σ = 7mos 
manufacturer does not want to exchange more than 10% of the watches

  z = 1.282 represents 10% of the Standard Normal Curve
  
 
    x = 7(1.282) + 48 = 56.97 (rounding down to 56)  
90% are expected to have lifetime of 56mo
 For how many months should a guarantee be made:  56mo
Wish You the Best in your Studies.


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