bright dataset

Brightness of de-inked newspaper

One step of recycling newsprint is to "de-ink" the newsprint, that is to remove the ink. The brightness of the paper pulp after a de-inking process is a measure of how well the process to remove the ink worked. A half-fraction of a $2^5$ factorial experiment experiment was run to test various factors on the ability to de-ink newsprint. 1.1

data

data(bright)

Format

A data frame with 16 observations on the following 6 variables.

• type: type of alkali - an ordered factor with levels A < B
• percent: percentage of alkali (25% or 75%)
• time: time pulp is soaked (30 or 40 minutes)
• hardness: water hardness (150 or 250)
• speed: agitation rate - an ordered factor with levels S < F
• bright: Brightness of pulp

References

Peter R. Nelson, Marie Coffin and Karen A. F. Copeland (2003), Introductory Statistics for Engineering Experimentation, Elsevier. (Appendix A)

Examples

str(bright)
options(contrasts = c("contr.treatment", "contr.helmert"))
summary(fm1 <- lm(bright ~ (type + percent + time + hardness + speed)^2,
                  bright))
qqmath(coef(fm1)[-1], aspect = 1,
       panel = function(...)
   {
       panel.grid(h = -1, v = -1)
       panel.qqmath(...)
       panel.qqmathline(..., alpha = 0.5, lty = 2)
   },
       xlab = "Standard normal quantiles",
       ylab = "First- and second-order effects")
summary(fm2 <- lm(bright ~ (type + hardness)^2, bright))
dotplot(type ~ bright, bright, groups = hardness,
        type = c("p", "a"), jitter.y = TRUE,
        xlab = "Brightness of pulp (lines and point styles are levels of water hardness)",
        ylab = "Alkali type", aspect = 0.4,
        auto.key = list(lines = TRUE, columns = 2))