Tobacco data from Snedecor and Cochran (1967)

Description

This dataset presents 8 paired data corresponding to numbers of lesions caused by two virus preparations inoculated into the two halves of each tobacco leaves.

Usage

data(Tobacco)

Format

A dataframe with 8 rows and 3 columns:

Source

Snedecor, G.W. and Cochran, W.G. (1967) Statistical Methods, 6th ed. Iowa State University Press: Ames.

References

• Pruzek, R.M. & Helmreich, J.E. (2009) Enhancing dependent sample analysis with graphics. Journal of Statistics Education, 17 (1).

• Preece, D.A. (1982) t is for trouble (and textbooks): a critique of some examples of the paired-samples t-test. The Statistician, 31 (2), 169-195.

Examples

data(Tobacco)

# A clear outlier
with(Tobacco,plot(paired(Preparation_1,Preparation_2)))


# Comparison of normal and robust tests
with(Tobacco,t.test(paired(Preparation_1,Preparation_2)))
with(Tobacco,yuen.t.test(paired(Preparation_1,Preparation_2)))

with(Tobacco,Var.test(paired(Preparation_1,Preparation_2)))
with(Tobacco,grambsch.Var.test(paired(Preparation_1,Preparation_2)))

with(Tobacco,cor.test(Preparation_1,Preparation_2))
with(Tobacco,winsor.cor.test(Preparation_1,Preparation_2))

# Maybe a transformation
require(MASS)
with(Tobacco,eqscplot(log(Preparation_1),log(Preparation_2)))
abline(0,1,col="red")