Return to Homework 02
This signifies that this practice. Although the act of completing a project (or mostly completing it—you won’t write a report) will be graded. We want this project to be more about learning the process of doing an analysis project, making decisions and documenting them. We will hold your hand a little more for this project. In that way it isn’t as formal as projects 1-3…which got real numbers.
Dental researchers were interested in a new gel treatment for gum disease. In their study, subjects were randomly assigned to one of 5 treatments: no treatment and four levels of an active substance in a gel. The lowest level was a placebo (=1) and then another control group (=2), like the “no treatment” group. The remaining three levels were low(=3), medium(=4), and high(=5) concentrations of the active ingredient in the gel. The patients were recruited via a single midwestern dental research clinic. There were 130 participants. Participants were asked to rub the gel on their gums twice daily. The measurements being followed over time were whole-mouth average pocket depth and whole mouth average attachment loss. Visits were at baseline and 1 year. Pocket depth and attachment loss were measured at many sites within each participant’s mouth and then averaged (at each visit). The variable called “sites” gives the number of sites used in the averages. Pocket depth and attachment loss are both measures of how far the gums have pulled away from the teeth, hence smaller values are better. Whole-mouth average is used because the measurements within mouth are highly correlated in a complicated way, which is not yet fully understood by dental researchers. Additional demographic information was collected on race(5=white,4=Asian,2=African American,1=Native American), gender(1=male,2=female), age, and smoking status (yes=1/no=0). Site is the number of sites measured to get the average outcome measurement. Missing values are denoted by an “NA”.
The primary question of interest is whether treatment results in lower average pocket depth and attachment loss at one year.