Statistics Tutor: None Selected Time limit: 1 Day

The lifetime of a certain brand of battery is known to have a standard deviation of 19.8 hours. Suppose that a random sample of 70 such batteries has a mean lifetime of 35.8 hours. Based on this sample, find a 90% confidence interval for the true mean lifetime of all batteries of this brand. Then complete the table below.

Carry your intermediate computations to at least three decimal places. Round your answers to one decimal place.

Jun 21st, 2015

using for confidence interval IC= Z*s/n^0.5; z for 90% is 1.28; you have n= 70 and  s=19.8

so the IC is 3.029 hours, so

a) the lower limit is 19.8-3.029=16.771 hr

b) the upper limit is 19.8+3.029=22.829 hr

Jun 21st, 2015

Jun 21st, 2015

sorry, it is because of time was running out since the system has own time. The rounded off  answers are

a) the lower limit is 19.8-3.029=16.8 hr

b) the upper limit is 19.8+3.029=22.8 hr

Feel free to ask more questions on statistics.

Jun 21st, 2015

Thank you!

Jun 21st, 2015

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Jun 21st, 2015
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Jun 21st, 2015
Dec 6th, 2016
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