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A company wants to know the useful life of a new revolutionary lightbulb it has just...

  1. A company wants to know the useful life of a new revolutionary lightbulb it has just developed. A mean of 64 of these bulbs revealed a mean useful life of 30,000 with a standard deviation of 1,500 hours.
  1. Use this information to develop a 95% confidence interval for the mean useful life of all new revolutionary lightbulbs.
  1. Use this information to develop a 98% confidence interval for the mean useful life of all new revolutionary lightbulbs.
Math   Statistics-And-Probability   
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Answer #1

Since , the population standard deviation is not known.

Therefore , use t-distribution

Now , df=degrees of freedom=n-1=64-1=63

A. Now , ; The Excel function is , =TINV0.05,63)

Therefore , the 95% confidence interval for the mean useful life of all new revolutionary lightbulbs is ,

B. Now , ; The Excel function is , =TINV0.02,63)

Therefore , the 98% confidence interval for the mean useful life of all new revolutionary lightbulbs is ,

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