Data set: Hodgkins
The data set Hodgkins contains plasma bradykininogen levels (in micrograms of bradykininogen per milliliter of plasma) in three types of subjects (normal, patients with active Hodgkin’s disease, and patients with inactive Hodgkin’s disease). The globulin bradykininogen is the precursor sub-stance for bradykinin, which is thought to be a chemical mediator of inflammation.
a. Create individual value plots or side-by-side boxplots of the bradykininogen levels for each group. Compare the mean and standard deviation of each group. Do the data within each group look consistent with data from a normal population?
b. Calculate the ANOVA model estimates in order to create a normal probability plot of the residuals. Do the error terms look consistent with data from a normal population?
c. Transform the data by taking the log of the response. Create individual value plots or side-by-side boxplots of the transformed responses. Compare the mean and standard deviation of each group. Do the transformed data within each group look consistent with data from a normal population?
d. Calculate the ANOVA model estimates using the transformed data in order to create a normal probability plot of the residuals. Do the error terms look consistent with data from a normal population? You may have to try out more than one transformation before you are satisfied with your answer to this part and Part C.
e. Using the transformed data, calculate an ANOVA table, F-test, and p-value to determine if the three patient types differed in their mean bradykininogen levels.