Drying times of concrete

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Description

Drying times of different concrete mixes used in a sidewalk. Mix ‘A’ is the conventional mix. Mixes ‘B’ and ‘C’ are experimental, and more expensive, mixes.

Format

A data frame with 19 observations on the following 2 variables.

type

concrete mix - a factor with levels A, B and C

time

time (hr) until concrete is dry enough to walk on

References

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

Examples

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str(cement)
dotplot(reorder(type, time) ~ time, cement, type = c("p","a"),
        jitter.y = TRUE, ylab = "Mix type",
        xlab = "Time until concrete is dry enough to walk on (hours)")
qqmath(~ time, cement, groups = type, aspect = 'xy',
       xlab = "Standard normal quantiles",
       type = c("g","p"),
       panel=function(...)
   {
       panel.qqmathline(..., alpha = 0.5, lty = 2)
       panel.qqmath(...)
   },
       ylab = "Time until concrete is dry enough to walk on (hours)",
       auto.key = list(space = "right", title = "Type", lines = TRUE))
summary(fm1 <- aov(time ~ type, cement))
TukeyHSD(fm1)

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