Use technology to construct the confidence intervals for the population variance σ2 and the population standard deviation σ. Assume the sample is taken from a normally distributed population.c=0.99, s=33, n=16The confidence interval for the population variance is □, □. (Round to two decimal places as needed.)
Q. Use technology to construct the confidence intervals for the population variance σ2 and the population standard deviation σ. Assume the sample is taken from a normally distributed population.c=0.99, s=33, n=16The confidence interval for the population variance is □, □. (Round to two decimal places as needed.)
Calculate degrees of freedom: Use the chi-square distribution to find the critical values for the confidence interval of the population variance. The degrees of freedom (df) is n−1.df=n−1=16−1=15
Find chi-square critical values: Find the chi-square critical values using a chi-square table or technology for df=15 and c=0.99. The lower critical value (chi-square left) corresponds to the upper tail and the upper critical value (chi-square right) corresponds to the lower tail because the chi-square distribution is not symmetric.χ2(0.005,15)χ2(0.995,15)
Use formula for confidence interval: Plug the critical values and the sample standard deviation into the formula for the confidence interval of the population variance.Confidence interval for variance = [(n−1)⋅s2]/χright2,[(n−1)⋅s2]/χleft2
Calculate confidence interval: Calculate the confidence interval using the sample standard deviation s=33 and the sample size n=16. Confidence interval for variance = [15×(33)2]/χright2,[15×(33)2]/χleft2
Find exact chi-square critical values: Use technology to find the exact chi-square critical values.χ2(0.005,15)≈5.23χ2(0.995,15)≈30.58
Substitute critical values: Substitute the critical values into the confidence interval formula.Confidence interval for variance = [(15)×(33)2]/30.58, [(15)×(33)2]/5.23
Perform calculations: Perform the calculations to find the confidence interval for the population variance.Confidence interval for variance = [30.58(15)×(1089),5.23(15)×(1089)]Confidence interval for variance = [30.5816335,5.2316335]Confidence interval for variance ≈534.16,3124.28
Round variance interval: Round the confidence interval for the population variance to two decimal places.Confidence interval for variance ≈534.16,3124.28
Calculate square roots: To find the confidence interval for the population standard deviation, take the square root of the variance interval endpoints.Confidence interval for standard deviation = 534.16, 3124.28
Round standard deviation interval: Calculate the square roots.Confidence interval for standard deviation ≈23.11,55.89
Round standard deviation interval: Calculate the square roots.Confidence interval for standard deviation ≈23.11,55.89Round the confidence interval for the population standard deviation to two decimal places.Confidence interval for standard deviation ≈23.11,55.89
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