toothbrush {GLMsData} | R Documentation |
Effectiveness of toothbrushes
Description
The effectiveness of two types of toothbrushes for males and females
Usage
data(toothbrush)
Format
A data frame with 52 observations on the following 5 variables.
Subject
an identifier
Sex
the sex of the subject; a factor with levels
F
(female) orM
(male)Toothbrush
the type of toothbrush; a factor with levels
Hugger
orConventional
Before
the dental plaque index before brushing; a numeric vector
After
the dental plaque index after brushing; a numeric vector
Details
The data give the plaque index before and after brushing for
two types of toothbrushes for males and females.
Each subject uses both toothbrushes.
A dental plaque index of zero is the best possible score;
brushing cannot make the score worse;
Before - After
is positive continuous with one exact zero.
Source
Reiko Aoki, Jorge A. Achcar, Heleno Bolfarine, and Julio M. Singer (2003) Bayesian analysis of null-intercept errors-in-variables regression for pretest/post-test data. Journal of Applied Statistics, 30(1), 3–12.
References
J. M. Singer and D. F. Andrade (1997) Regression models for the analysis of pretest-posttest data. Biometrics, 53, 729–735.
Examples
data(toothbrush)
with(toothbrush, plot(Before-After ~ Sex) )
with(toothbrush, plot(Before-After ~ Toothbrush) )