SOLUTION: The lifetime of TV picture tube is normally distributed with mean 8 years ans standard deviation 2 years. 1) What is the probability it will last more than 10 years 2) If it has 4

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Question 853786: The lifetime of TV picture tube is normally distributed with mean 8 years ans standard deviation 2 years. 1) What is the probability it will last more than 10 years 2) If it has 4 years guarntee what % of tube sold will be replaced.
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
The lifetime of TV picture tube is normally distributed with mean 8 years ans standard deviation 2 years.
1) What is the probability it will last more than 10 years
z(10) = (10-8)/2 = 1
P(x > 10) = P(z > 1) = 0.1587
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2) If it has 4 years guarantee what % of tube sold will be replaced.
z(4) = (4-8)/2 = -2
P(x < 4) = P(z < -2) = 0.0228 = 2.28%
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Cheers,
Stan H.
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