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A car manufacturing company is evaluating the effect of a new engine design on fuel efficiency. A random sample of 55 cars is assembled using the new design, and their miles per gallon (mpg) are recorded. The mpg values are assumed to be normally distributed with a known variance of 9. The sample mean mpg is found to be 32. Calculate the 99% confidence interval for the average mpg of all cars assembled with the new engine design. 

          A car manufacturing company is evaluating the effect of a new engine design on fuel efficiency. A random sample of 55 cars is assembled using the new design, and their miles per gallon (mpg) are recorded. The mpg values are assumed to be normally distributed with a known variance of 9. The sample mean mpg is found to be 32. Calculate the 99% confidence interval for the average mpg of all cars assembled with the new engine design.
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Elementary Statistics a Step by Step Approach
Elementary Statistics a Step by Step Approach
Allan G. Bluman 9th Edition
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A car manufacturing company is evaluating the effect of a new engine design on fuel efficiency. A random sample of 55 cars is assembled using the new design, and their miles per gallon (mpg) are recorded. The mpg values are assumed to be normally distributed with a known variance of 9. The sample mean mpg is found to be 32. Calculate the 99% confidence interval for the average mpg of all cars assembled with the new engine design.
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Transcript

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00:02 To construct a confidence interval for the true average miles per gallon of the hybrid model, you can use the formula for the confidence interval of population mean.
00:10 This formula for the confidence interval is the sample mean plus or minus the critical z times the sample standard deviation, which is the sample size.
00:17 In this case, the sample mean is 45 miles per gallon.
00:20 The critical z for 95 % from the standard normal table is 1 .96...
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