Refer to the data of Exercise 12.9. Often a logarithmic transformation can be used on the dose…
Refer to the data of Exercise 12.9. Often a logarithmic transformation can be used on the dose levels to linearize the response with respect to the independent variable.
a. Obtain the natural logarithms of the five dose levels, ln(dose)
b. Let ln(dose), fit the model
c. Compare your results to the fitted models in Exercise 12.9. Does the logarithmic transformation provide a better fit than the models in Exercise 12.9?
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 linear and quadratic regression models to these data.
c. Which regression equation appears to fit the data better? Why?