Problem

A manufacturer tested the abrasive effect of a wear tester for experimental fabrics on a p...

A manufacturer tested the abrasive effect of a wear tester for experimental fabrics on a particular fabric while run at six different machine speeds. Forty-eight identical 5-inch-square pieces of fabric were cut, with eight squares randomly assigned to each of the six machine speeds, 100, 120, 140, 160, 180, and 200 revolutions per minute (rev/min). The order of assignment of the squares to the machine was random, with each square tested for a 3-minute period at the appropriate machine setting. The amount of wear was measured and recorded for each square. The data appear here.

a. Generate a graph of the data. (The variability within a speed is about the same for all speeds, so you can save time while still maintaining the trend by plotting the sample mean for each speed.)
b. What type of regression model appears appropriate?
c. Output for linear, quadratic, and cubic regression models is shown on the following pages. Which regression equation gives a better fit? Why?
d. Is there anything peculiar about the data? What might have happened?

LINEAR REGRESSION ANALYSIS FOR WEAR TESTER DATA