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anonymous
 5 years ago
A random sample of 105 light bulbs had a mean life of 441 hours with a standard deviation of 40 hours. Construct a 90% confidence interval for the mean life, mu, of all light bulbs of this type.
anonymous
 5 years ago
A random sample of 105 light bulbs had a mean life of 441 hours with a standard deviation of 40 hours. Construct a 90% confidence interval for the mean life, mu, of all light bulbs of this type.

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anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0The CIE is (434.58 , 447.42)

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0A zscore of ~1.645 will give a twotailed confidence level of ~0.9 = 90%. \[z = \frac{x  \mu}{\sigma}\] \[z*\sigma = x  \mu\] Where z is the zscore, sigma is the standard deviation, \mu is the mean, and x is the picked score. Solve for both values of x.

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0Just notices that the standard deviation is that of the sample and not the whole population, therefore this must be done with a Tvalue instead of a Zvalue... so my answer above is incorrect. The 90% CIE should actually be (434.52 , 447.48)
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