A pharmaceutical firm would like to obtain information on the relationship between the d...

A pharmaceutical firm would like to obtain information on the relationship between the dose level and potency of a drug product. To do this, each of 15 test tubes is inoculated with a virus culture and incubated for 5 days at 30° C. Three test tubes are randomly assigned to each of the five different dose levels to be investigated (2, 4, 8, 16, and 32 mg). Each tube is injected with only one dose level and the response of interest (a measure of the protective strength of the product against the virus culture) is obtained. The data are given here.

a. Plot the data.

b. Fit a linear regression model to these data.

c. What other regression model might be appropriate?

d. SAS computer output is shown for both a linear and quadratic regression equation. Which regression equation appears to fit the data better? Why?