EngrExpt (version 0.1-8)

sarea: Surface area of silica

Description

Measurements of the surface area ($m^2/g$) of three batches of silica as performed by four different lab technicians.

Format

A data frame with 12 observations on the following 3 variables.

batch

a factor with levels a, b and c

tech

a factor with levels A, B, C and D

sarea

the surface area in $m^2/g$ as measured by the lab technician on a sample from the batch

References

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

Examples

str(sarea)
xtabs(sarea ~ batch + tech, sarea)
dotplot(reorder(tech, sarea) ~ sarea, sarea,
        groups = batch, type = c("p","a"), aspect = "xy",
        ylab = "Technician",
        xlab = expression("Measured surface area " * (m^2/g) *
                          " of silica batches"),
        auto.key = list(columns = 3, lines = TRUE)
)