The height of a solution containing a “defoamer” in a 50-ml graduated cylinder after being heated to a particular temperature.
A data frame with 27 observations on the following 4 variables.
concentration of defoamer - a factor with levels
pH of defoamer - a factor with levels
temperature of defoamer - a factor with levels
height of solution in the graduated cylinder
A defoamer is a product that controls the formation of foam in industrial processes such as one might find in the food industry.
Peter R. Nelson, Marie Coffin and Karen A. F. Copeland (2003), Introductory Statistics for Engineering Experimentation, Elsevier. (Appendix A)
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str(defoam) dotplot(pH ~ height|conc, defoam, groups = temp, aspect = 0.3, xlab = "Height of solution", type = c("p","a"), auto.key = list(space = "right", lines = TRUE, title = "Temperature"), strip = FALSE, strip.left = TRUE, ylab = "pH within concentration") summary(fm1 <- lm(height ~ (conc + pH + temp)^2, defoam)) summary(fm2 <- lm(height ~ (pH + temp)^3, defoam))