Question: Testing a new pain-reliever tablet. Paracetamol is the active ingredient in drugs designed to relieve mild to moderate pain and fever. The properties of paracetamol tablets derived from khaya gum were studied in the Tropical Journal of Pharmaceutical Research (June 2003). Three factors believed to impact the properties of paracetamol tablets are (1) the nature of the binding agent, (2) the concentration of the binding agent, and (3) the relative density of the tablet. In the experiment, binding agent was set at two levels (khaya gum and PVP), binding concentration at two levels (.5% and 4.0%), and relative density at two levels (low and high). One of the dependent variables investigated in the study was tablet dissolution time, that is, the amount of time (in minutes) for 50% of the tablet to dissolve. The goal of the study was to determine the effect of binding agent, binding concentration, and relative density on mean dissolution time.
(a) Identify the dependent (response) variable in the study.
(b) What are the factors investigated in the study? Give the levels of each.
(c) What type of experimental design was employed?
(d) How many treatments are possible in the study? List them.
(e) Write the linear model appropriate for analyzing the data.
(f) The sample mean dissolution times for the treatments associated with the factors binding agent and relative density when the other factor (binding concentration) is held fixed at .5% are: Y¯ Gum/Low = 4.70, Y¯ Gum/High = 7.95, Y¯ PVP/Low = 3.00, and Y¯ PVP/High = 4.10. Do the results suggest there is an interaction between binding agent and relative density? Explain.