a. Is a linear model appropriate for Data Set A? Justify your answer using Residual Plot A.
b. What does Residual Plot B reveal about the reliability of the estimates from the regression line in
Data Set B?
c. Explain what information is being conveyed about the linear regression for Data Set C in Residual
Plot C.
New formulas of gel nail polish have recently been introduced. A local salon wished to test number
of days of wear of the new formula against the old formula as a control. Identical bottles of both
formulas are prepared and 14 clients have their nails polished on their first visit with one formula
(chosen at random) and then the next visit with the other formula. The number of days of wear is then
compared.
Do these data provide evidence that the mean number of days of wear is greater for the new formula
of gel nail polish than for the old? Use α = 0.05.Statistics, Section II, Part B, Question 6
Spend about 25 minutes on this part of the exam; percentage of Section II grade: 25.
Directions: Show all of your work. Indicate clearly the methods you use because you will be graded
on the correctness of your methods as well as on the accuracy of your results and explanation.
Overuse of lawn chemicals causes environmental problems when runoff gets into waterways.
Researchers tested three types of fertilizer spreaders typically used by homeowners: drop spreaders,
hand-held broadcast rotary spreaders, and push rotary spreaders. The goal was to determine if the
type of spreader influenced the ability of the user to apply the correct amount of fertilizer.
Fifteen volunteers who were homeowners with no particular training in the use of this equipment
operated the spreaders. Each spreader was randomly assigned to a 1,000-square-foot plot of lawn.
The researchers prepared the spreaders by correctly setting the dispensation amount and providing the
same amount of fertilizer in each spreader. The spreader with fertilizer was weighed before and after
the fertilizer was applied to determine the amount dispensed.
a. What were the experimental units? The treatments? The response variable?
The plot below shows the amounts dispensed by each type of spreader in kg/100 m^2 .