An important quality characteristic used by the manufacturer ofBoston and Vermont asphalt shingles is the amount of moisture theshingles contain when they are packaged. Customers may feel thatthey have purchased a product lacking in quality if they findmoisture and wet shingles inside the packaging. In some cases,excessive moisture can cause the granules attached to the shinglesfor texture and coloring purposes to fall off the shingles,resulting in appearance problems. To monitor the amount of moisturepresent, the company conducts moisture tests. A shingle is weighedand then dried. The shingle is then re-weighed, and, based on theamount of moisture taken out of the product, the pounds of moistureper 100 square feet are calculated. The company would like to showthat the mean moisture content is less than 0.35 pound per 100square feet. The file Moisture includes 36 measurements ( in poundsper 100 square feet) for Boston shingles and 31 for Vermontshingles.
e. What assumption about the population distribution is neededin order to conduct the t tests in ( a) and ( c)?
f. Construct histograms, boxplots, or normal probability plotsto evaluate the assumption made in ( a) and ( c).
g. Do you think that the assumption needed in order to con-ductthe t tests in ( a) and ( c) is valid? Explain.
