CSC 239: Personal Computing for Science

Third Assignment (Due 11:30pm Monday October 10, 2005)

Assignment

Open a new workbook. Download the file cereals.txt and save it in your work directory. The file contains data on several variables of 77 different brands of cereal. The variables are

• name: name of cereal,
• calories: calories per serving,
• protein: grams of protein,
• fat: grams of fat,
• sodium: milligrams of sodium,
• carbo: grams of complex carbohydrates,
• sugars: grams of sugars,
• shelf: display shelf (1, 2, or 3, counting from the floor), and
• rating: a rating of the cereals.

Please perform the following steps on the data:

1. Import the data into an Excel workbook. Label the sheet containing the data "Data".
2. Using Excel, draw a histogram for the sugar content per serving. (Choose an appropriate bin range.) Put the histogram on a sheet named "Histogram".
3. Describe the distribution of the data; is the histogram symmetric or skewed? Answer this question on the Histogram worksheet.
4. Using the worktable for computing confidence intervals we created in class (you will also create a table in lab too), compute the 95% confidence interval of the average sugar content per serving in cereals sold in the US. Put the worktable on a sheet named "Confidence".
5. Explain to somebody who knows no statistics what the computed result represents. Put your answer on the Confidence worksheet.
6. Using either the same worktable or a new one, give a 98% confidence interval for the average sodium content of the cereals. Put this answer also on the Confidence worksheet.
7. A nutritionist claims that cereals contain 140 milligrams of sodium on average. Is this claim confirmed by your data? Why or why not? Finally, put the answer on the Confidence worksheet.

Additional challenge

Are low-fat cereals also low in sugars? Divide the cereals into low-fat and high fat categories so that there are a meaningful number of cereals in each category (you should work out and provide the details). Report on the average amount of sugars in each category and provide confidence intervals. Consider using a pivot table for your analysis.

Deliverables

Submit your excel workbook using Course On-Line. Make sure that text answers are included in your workbook as indicated above.