Kidney failure patients are commonly treated on dialysis machines that filter
toxic substances from the blood. The appropriate "dose" for effective
treatment depends, among other things, on duration of treatment and weight
gain between treatments as a result of fluid buildup. To study the effects of
these two factors on the number of days hospitalized (attributable to the
disease) during a year, a random sample of '10 patients per group who had
undergone treatment at a large dialysis facility was obtained. Treatment
duration (factor \(A\) ) was categorized into two groups: short duration
(average dialysis time for the year under four hours) and long duration
(average dialysis time for the year equal to or greater than four hours).
Average weight gain between treatments (factor \(B\) ) during the year was
categorized into three groups: slight, moderate, and substantial. The data on
number of days hospitalized follow.
The transformed data \(Y^{\prime}=\log _{10}(Y+1)\) are to be used for the
analysis.
a. Obtain the fitted values and residuals for ANOVA model (19.23) for the
transformed data.
b. Prepare aligned residual dot plots for the treatments. What departures from
ANOVA model (19.23) can be studied from these plots? What are your findings?
c. Prepare a normal probability plot of the residuals. Also obtain the
coefficient of correlation between the ordered residuals and their expected
values under normality. Does the normality assumption appear to be reasonable
here?