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Company A claims that its light bulbs are superior to those from company B. A study...

Company A claims that its light bulbs are superior to those from company B. A study shows that a sample of 40 bulbs from company A has a mean lifetime 647 hours of continuous use with a standard deviation of 27 hours, while a sample of 40 bulbs from company B had a mean life time of 638 hours of continuous use with a standard deviation of 31 hours. Calculate the 83% confidence interval for the difference of the two means.   

Math   Statistics-And-Probability   
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Answer #1

therefore, 83% confidence interval for difference of two mean is ( 2.80 , 15.20).

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