Question 1047126: Can someone please check to see if this is done correctly?
1. A random sample of size 64 has sample mean 24 and sample standard deviation 4.
a. Is it appropriate to use the t distribution to compute a confidence interval for the population mean? Why or why not? No, because our sample size is more than 30.
b. Construct a 95% confidence interval for the population mean.
22.1 < µ < 25.9
2. You are trying to estimate the average miles per gallon for a new brand of car. A random sample of 40 cars, and, for this sample, the average miles per gallon is 32 and the standard deviation is 2.2.
a. Suppose you would like to construct a 90 percent confidence interval. What would be the margin of error for this interval?
1.645(2.2 / √40) ≈ 0.57
b.What would be the lower and upper limits for this 90 percent confidence interval?
31.43 < µ < 32.57
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! 1. A random sample of size 64 has sample mean 24 and sample standard deviation 4.
a. Is it appropriate to use the t distribution to compute a confidence interval for the population mean? Why or why not? No, because our sample size is more than 30.
b. Construct a 95% confidence interval for the population mean.
sample mean = 24
ME = 1.96*4/sqrt(24) = 1.6
95%CI:: 24-1.6 < u < 25.6
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2. You are trying to estimate the average miles per gallon for a new brand of car. A random sample of 40 cars, and, for this sample, the average miles per gallon is 32 and the standard deviation is 2.2.
a. Suppose you would like to construct a 90 percent confidence interval. What would be the margin of error for this interval?
1.645(2.2 / √40) ≈ 0.57
b.What would be the lower and upper limits for this 90 percent confidence interval?
31.43 < µ < 32.57
OK
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Cheers,
Stan H.
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