SOLUTION: Jessica Salas, president of Salas Products, is reviewing the warranty policy for her company's new model of automobile batteries. Life tests performed on a sample of 100 batteries

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Question 462324: Jessica Salas, president of Salas Products, is reviewing the warranty policy for her company's new model of automobile batteries. Life tests performed on a sample of 100 batteries indicated: (1) an average life of 75 months, (2) a standard deviation of 5 months, and (3) a bell shaped battery life distribution. What percentage of the batteries will fail within the first 65 months of use?


Answer by edjones(8007) About Me  (Show Source):
You can put this solution on YOUR website!
mu=75+sigma=5
z=%28x%5Bi%5D-mu%29%2Fsigma=%2865-75%29%2F5=-10%2F5=-2
Area under the normal curve below z=-2 is .023 = 2.3% of the batteries will fail within the first 65 months of use.
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Ed