Question 136541
The lifetime of a certain brand of battery is known to have a standard deviation of 23 hours. Suppose that a random sample of 70 such batteries has a mean lifetime of 35.1 hours. Based on this sample, find a 95% confidence interval for the true mean lifetime of all batteries of this brand.
x-bar = 35.1
E = 1.96*[23/sqrt(70)] = 5.38801...
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95% CI:(35.1-5.38801 < u < 35.1+5.38801)
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Cheers,
Stan H.