Estimating From Samples
For this assessment, you will need to use SAS Enterprise Guide or the Excel Calculators, the latter of which can be found in Resources. SAS users can reference the SAS tutorials located in the third study activity of Unit 1. For this assignment, you will practice applying inferential statistical analysis to two business decision scenarios. Complete both of the following scenarios.
Practical Application Scenario 1
To complete this scenario, use SAS Enterprise Guide or the Confidence Interval Calculator and the Area Gas Prices document, provided in Updates and Handouts.
TheStar Tribunenewspaper has decided to write an article about gasoline prices in the Twin Cities area (Minneapolis and St. Paul, Minnesota). The newspaper has designed a survey and taken a simple random sample of regular unleaded gas prices at 70 area stations. The results are in the Area Gas Prices file. The newspaper's policy is that no data will be reported unless they are 95 percent confident that the numbers are correct. As the new manager of the data verification unit at theStar Tribune, you need to develop a 95 percent confidence interval for the average price of regular unleaded gasoline in the Twin Cities area.
You already know how to compute sample parameters, like the sample mean and sample standard deviation; this scenario simply asks you to complete a confidence interval for the data provided and communicate the results to theStar Tribune's business manager.
Practical Application Scenario 2
To complete this scenario, use the Sample Size Estimator file provided in Resources.
The third shift at the Microsoft's Windows security unit in Redmond, Washington is considering replacing its coffee brewing units with new German-made brewers. As the newest member of this elite Microsoft team, you have been assigned to investigate this proposal. Develop a 99 percent confidence interval for the average yield (cups per pound) for the new German coffee brewer. The margin of error should be no bigger than 0.3 (three tenths of a cup). Based on experience with the current coffee makers, your best guess for the population standard deviation, sigma, is 1.2 cups. How big of a sample do you need? Calculate the estimated sample size needed for the above scenario and communicate your findings to the business manager.
Compile the two practical application scenario answers into one Word file (submitted as a .docx file) and copy the Excel or SAS output into that document. Highlight your numerical answers for both practical applications scenarios in yellow, and then right after that numerical solution, be sure to summarize your findings in a three- to five-sentence paragraph to the scenario manager.
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