A random sample of 32 retail stocks such as Toys ‘R’ Us, Best Buy , and Gap were studied for x1, profit as a percentage of stockholder equity. The result was ?̅1 = 13.7. A random sample of 34 utility (gas and electric) stocks such as Boston Edison, Wisconsin Energy, and Texas Utilities, were studied for x2, profit as a percentage of stockholder equity. The result was ?̅2 = 10.1. (Source: Fortune 500, Vol. 135, No. 8.) Assume that ?1 = 4.1 and ?2 = 2.7. a. Let ?1 represent the population mean profit as a percentage of stockholder equity for retail stocks, and let ?2 represent the population mean profit as a percentage of stockholder equity for utility stocks. Find a 95% confidence interval for ?1 − ?2 (by the calculator). b. Explain what this interval means in the context of this problem. Can we make any conclusion comparing μ1and μ2
A random sample of 32 retail stocks such as Toys ‘R’ Us, Best Buy , and Gap were studied for x1,
profit as a percentage of stockholder equity. The result was ?̅1 = 13.7. A random sample of 34
utility (gas and electric) stocks such as Boston Edison, Wisconsin Energy, and Texas Utilities, were
studied for x2, profit as a percentage of stockholder equity. The result was ?̅2 = 10.1. (Source:
Fortune 500, Vol. 135, No. 8.) Assume that ?1 = 4.1 and ?2 = 2.7.
a. Let ?1 represent the population mean profit as a percentage of stockholder equity for retail
stocks, and let ?2 represent the population mean profit as a percentage of stockholder equity
for utility stocks. Find a 95% confidence interval for ?1 − ?2 (by the calculator).
b. Explain what this interval means in the context of this problem. Can we make any conclusion
comparing μ1and μ2
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