Calcium levels before and after vitamin supplement

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Description

Calcium levels before and after vitamin supplement

Format

A data frame with 49 observations on the following 3 variables.

treatment

formulation - a factor with levels A, B and C

before

Calcium level before the vitamin

after

Calcium level after the vitamin

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(vitamin)
summary(vitamin)
show(plt1 <- xyplot(after ~ before, vitamin, groups = treatment,
       auto.key = list(space = "right", title = "Formulation", lines = TRUE),
       aspect = "iso",
       type = c("g","p","smooth"),
       xlab  = "Calcium level before the vitamin",
       ylab = "Calcium level after the vitamin"))
tmd(plt1, aspect = 1)
densityplot(~ I(after - before), vitamin, groups = treatment,
            auto.key = list(columns = 3, lines = TRUE),
            xlab = "Change in calcium level after taking vitamin")

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