# Does the test show enough evidence to reject the findings of Robert Half International?

cide to sample some fast-food restaurants currently operating to estimate the monthly cost of electricity. They want to be 99% confident of their results and want the error of the interval estimate to be no more than \$100. They estimate that such bills range from \$600 to \$2,500. How large of a sample should they take?

Question 2 Suppose a study reports that the average price for a gallon of self-serve regular unleaded gasoline is \$3.16. You believe that the figure is higher in your area of the country. You decide to test this claim for your part of the United States by randomly calling gasoline stations. Your random survey of 25 stations produces the following prices (all in \$). Assume gasoline prices for a region are normally distributed. Did the data you obtained provide enough evidence to reject the claim? Use a 1% level of significance. Make sure you clearly state both the null and the alternative hypotheses in full sentences. Following your calculations, clearly state the conclusion in the same manner (do not simply say “accept/reject null”) and explain how you arrived at this conclusion (based on which metrics).

3.27 3.29 3.16 3.2 3.37

3.3 3.33 3.19 3.3 3.34

3.16 3.27 3.27 3.09 3.35

3.15 3.23 3.14 3.05 3.35

3.21 3.14 3.14 3.07 3.1

Question 3 Where do CFOs get their money news? According to Robert Half International, 47% get their money news from newspapers, 15% get it from communication/colleagues, 12% get it from television, 11% from the internet, 9% from magazines, 5% from radio, and 1% do not know. Suppose a researcher wants to test these results. She randomly samples 67 CFOs and finds that 40 of them get their money news from newspapers. Does the test show enough evidence to reject the findings of Robert Half International? Use a = .05. Make sure you clearly state both the null and the alternative hypotheses in full sentences. Following your calculations, clearly state the conclusion in the same manner (do not simply say “accept/reject null”) and explain how you arrived at this conclusion (based on which metrics).