Use the following files, to complete both of the scenarios for this assessment:
- Confidence Interval Calculator.
- Area Gas Prices – Random Sample.
- Sample Size Estimator.
Practical Application Scenario 1
To complete this scenario, use the
Confidence Interval Calculator
and the
Area Gas Prices – Random Sample
files.
The Minneapolis
Star Tribune
newspaper has decided to write an article about gasoline prices in the Twin Cities area (Minneapolis and Saint Paul, Minnesota). The
Star Tribune
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 – Random Sample file. The
Star Tribune's
policy is that no data will be reported unless it is 95 percent confident that the numbers are correct. As the new manager of the data verification unit at the
Star Tribune, you need to develop a 95 percent confidence interval for the average price of regular unleaded gasoline in the area.
- Complete a confidence interval for the data provided, using tables to demonstrate your method and findings.
- Write a 3–5 sentence summary that communicates your results to the
Star Tribune's business manager.
Practical Application Scenario 2
To complete this scenario, use the
Sample Size Estimator
file.
The third shift at Microsoft 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 .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 large a sample do you need?
- Calculate the estimated sample size needed for the above scenario, using tables to demonstrate your method and findings.
- Write a 3–5 sentence summary that communicates your results to the business manager.
Additional Requirements
Compile your work for both scenarios in one Microsoft Word file:
- Paste in the tables you used.
- Clearly title your tables, including each row and column.
- Highlight the results of your data calculations within each table.
- Summarize your findings for each scenario in a 3–5 sentence paragraph below each table.