GLMsData (version 1.4)

toothbrush: 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) or M (male)

Toothbrush

the type of toothbrush; a factor with levels Hugger or Conventional

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.

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) )