Refer to the Business and Society (March 2011) study on the sustainability behaviors of CPA corporations, Exercise 6.12. Recall that the level of support for corporate sustainability (measured on a quantitative scale ranging from 0 to 160 points) was obtained for each in a sample of 992 senior managers at CPA firms. The accompanying Minitab printout gives 90% confidence intervals for both the variance and standard deviation of level of support for all senior managers at CPA firms.

a. Locate the 90% confidence interval for σ2 on the printout. Interpret the result.
b. Use the sample variance on the printout to calculate the 90% confidence interval for σ2. Does your result agree with the interval shown on the printout?
c. Locate the 90% confidence interval for s on the printout.
d. Use the result, part a, to calculate the 90% confidence interval for σ. Does your result agree with the interval shown on the printout?
e. Give a practical interpretation of the 90% confidence interval for σ.
f. What assumption about the distribution of level of support is required for the inference, part e, to be valid? Is this assumption reasonably satisfied?

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Statistica N SeDev Variance Variable Support 992 26.9 722 901 Canfidence Intervala CI for Stbev CI for Variance (672, 779) Variable Method Support Chi-Square (25.9, 27.9)