SOLUTION: The standard deviation of test scores on a certain achievement test is 10.5 . A random sample of scores on this test had a mean of 72.8. Based on this sample, find a 90% confidence

Question 348451: The standard deviation of test scores on a certain achievement test is 10.5 . A random sample of scores on this test had a mean of 72.8. Based on this sample, find a 90% confidence interval for the true mean of all scores. Then complete the table below.
Carry your intermediate computations to at least three decimal places. Round your answers to one decimal place.
The lower limit of 90% confidence interval =
The upper limit of 90% confidence interval =

Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
The standard deviation of test scores on a certain achievement test is 10.5 . A random sample of scores on this test had a mean of 72.8. Based on this sample, find a 90% confidence interval for the true mean of all scores. Then complete the table below.
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x-bar = 72.8
E = (invNorm(0.95))*10.5 = 1.645*10.5 = 17.27
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Carry your intermediate computations to at least three decimal places. Round your answers to one decimal place.
The lower limit of 90% confidence interval = 72-17.27
The upper limit of 90% confidence interval = 72+17.27
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Cheers,
Stan H.
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