Submit your work using Microsoft Excel.
Chapter 9 Problems: 9.76, 9.77
Chapter 10 Problems: 10.61,10.62,10.63
9.76 An important quality characteristic used by the manufacturer of Boston and Vermont asphalt shingles is the amount of moisture the shingles contain when they are packaged. Customers may feel that they have purchased a product lacking in quality if they find moisture and wet shingles inside the packaging. In some cases, excessive moisture can cause the granules attached to the shingles for texture and coloring purposes to fall off the shingles, resulting in appearance problems. To monitor the amount of moisture present, the company conducts moisture tests. A shingle is weighed and then dried. The shingle is then reweighed, and based on the amount of moisture taken out of the product, the pounds of moisture per 100 square feet are calculated. The company would like to show that the mean moisture content is less than 0.35 pound per 100 square feet. The file Moisture includes 36 measurements (in pounds per 100 square feet) for Boston shingles and 31 for Vermont shingles.
A. For the Boston shingles, is there evidence at the 0.05 level of significance that the population mean moisture content is less than 0.35 pound per 100 square feet?
B. Interpret the meaning of the p-value in (a).
C. For the Vermont shingles, is there evidence at the 0.05 level of significance that the population mean moisture content is less than 0.35 pound per 100 square feet?
D. Interpret the meaning of the p-value in (c).
E. What assumption about the population distribution is needed in order to conduct the t tests in (a) and (c)?
F. Construct histograms, boxplots, or normal probability plots to evaluate the assumption made in (a) and (c).
G. Do you think that the assumption needed in order to conduct the t tests in (a) and (c) is valid? Explain.
9.77 Studies conducted by the manufacturer of Boston and Vermont asphalt shingles have shown product weight to be a major factor in the customer’s perception of quality. Moreover, the weight represents the amount of raw materials being used and is therefore very important to the company from a cost standpoint. The last stage of the assembly line packages the shingles before the packages are placed on wooden pallets. Once a pallet is full (a pallet for most brands holds 16 squares of shingles), it is weighed, and the measurement is recorded. The file Pallet contains the weight (in pounds) from a sample of 368 pallets of Boston shingles and 330 pallets of Vermont shingles.
A. For the Boston shingles, is there evidence at the 0.05 level of significance that the population mean weight is different from 3,150 pounds?
B. Interpret the meaning of the p-value in (a).
C. For the Vermont shingles, is there evidence at the 0.05 level of significance that the population mean weight is different from 3,700 pounds?
D. Interpret the meaning of the p-value in (c).
E. In (a) through (d), do you have to be concerned with the normality assumption? Explain.
10.61 The file Restaurants contains the ratings for food, décor, service, and the price per person for a sample of 50 restaurants located in a center city and 50 restaurants located in an outlying area. Completely analyze the differences between center city and outlying area restaurants for the variables food rating, décor rating, service rating, and cost per person, using a=0.05
10.62 A computer information systems professor is interested in studying the amount of time students in a programming course take to write a small Python program. The professor hires you to analyze the following results (in minutes), stored in Python, from a random sample of nine students:
10, 13, 9, 15, 12, 13, 11, 13, 12
A.. At the 0.05 level of significance, is there evidence that the population mean time is greater than 10 minutes? What will you tell the professor?
B. Suppose that the professor, when checking her results, realizes that the fourth student needed 51 minutes rather than the recorded 15 minutes to write the Python program. At the 0.05 level of significance, reanalyze the question posed in (a), using the revised data. What will you tell the professor now?
C. The professor is perplexed by these paradoxical results and requests an explanation from you regarding the justification for the difference in your findings in (a) and (b). Discuss.
D. A few days later, the professor calls to tell you that the dilemma is completely resolved. The original number 15 (the fourth data value) was correct, and therefore your findings in (a) are being used in the article she is writing for a computer journal. Now she wants to hire you to compare the results from that group of Introduction to Computers students against those from a sample of 11 computer majors in order to determine whether there is evidence that computer majors can write a Python program in less time than introductory students. For the computer majors, the sample mean is 8.5 minutes, and the sample standard deviation is 2.0 minutes. At the 0.05 level of significance, completely analyze these data. What will you tell the professor?
E. A few days later, the professor calls again to tell you that a reviewer of her article wants her to include the p-value for the “correct” result in (a). In addition, the professor inquires about an unequal-variances problem, which the reviewer wants her to discuss in her article. In your own words, discuss the concept of p-value and also describe the unequal-variances problem. Then, determine the p-value in (a) and discuss whether the unequal-variances problem had any meaning in the professor’s study.
10.63 Do social shoppers differ from other online consumers with respect to spending behavior? A study of browser-based shopping sessions reported that social shoppers, consumers who click away from social networks to retail sites or share an item on a social network, spent a mean of $126.12 on a retail site in a 30-day period compared to other online shoppers who spent a mean of $115.55.
