wash {EngrExpt}

Appearance of washed and unwashed panels

Description

Appearance ratings of washed and unwashed panels

Format

A data frame with 36 observations on the following 3 variables.

type

type of treatment - a factor with levels NW (not washed) and W (washed)

time1

initial rating

time2

rating after 2 weeks

Details

A particular durability test of paint involves applying drops of acid on the panel. After a particular time point the panel is rated for its ability to withstand the acid. This study involved washing (or not washing) panels and then storing them for two weeks to see if there was a residual effect of the acid on the panel. This was important as panels are often stored and used in presentations so the researchers needed to know if they should wash the panels before storing them.

References

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

Examples

str(wash)
summary(wash)
show(plt1 <- xyplot(time2 ~ time1, wash, groups = type,
       auto.key = list(columns = 2, lines = TRUE),
       aspect = "iso",
       type = c("g","p","smooth"),
       xlab  = "Initial rating",
       ylab = "Rating after 2 weeks",
       jitter.x = TRUE, jitter.y = TRUE))
tmd(plt1)
densityplot(~ I(time2 - time1), wash, groups = type,
            auto.key = list(columns = 2, lines = TRUE),
            xlab = "Change in rating after two weeks")