The data frame TIREWEAR contains measurements for the amount of tread loss in thousandths of an inch after 10,000 miles of driving.



A data frame with 16 observations on the following 3 variables:

  • wear (tread loss measured in thousandths of an inch)

  • treat (a factor with levels A, B, C, and D)

  • block (a factor with levels Car1, Car2, Car3, and Car4)


Ugarte, M. D., Militino, A. F., and Arnholt, A. T. 2015. Probability and Statistics with R, Second Edition. Chapman & Hall / CRC.


par(mfrow=c(1, 2), cex = 0.8) with(data = TIREWEAR, interaction.plot(treat, block, wear, type = "b", legend = FALSE)) with(data = TIREWEAR, interaction.plot(block, treat, wear, type = "b", legend = FALSE))
par(mfrow=c(1, 1), cex = 1)