xmp11.01 {Devore6} | R Documentation

## data from Example 11.1

### Description

The `xmp11.01` data frame has 12 rows and 3 columns from an experiment on the effect of different washing treatments in removing marks from an erasable pen.

### Format

This data frame contains the following columns:

strength
  a quantitative indicator of the overall specimen color change; the lower this value, the more marks were removed.
brand
  a numeric vector identifying the brand of erasable pen used.
treatment
  a numeric vector identifying the washing treatment.

### Details

### Source

Devore, J. L. (2003) Probability and Statistics for Engineering and the Sciences (6th ed), Duxbury

(1991), ``An assessment of the effects of treatment, time, and heat on the removal of erasable pen marks from cotton and cotton/polyester blend fabrics'', J. of Testing and Evaluation, 394-397.

### Examples

    data(xmp11.01)
    xmp11.01$brand <- factor(xmp11.01$brand)
    xmp11.01$treatment <- factor(xmp11.01$treatment)
    plot(strength ~ treatment, data = xmp11.01, col = "lightgray",
         main = "Interaction plot for Example 11.01",
         xlab = "Washing treatment")
    lines(strength ~ as.integer(treatment), data = xmp11.01,
          subset = brand == 1, col = 4, type = "b")
    lines(strength ~ as.integer(treatment), data = xmp11.01,
          subset = brand == 2, col = 2, type = "b")
    lines(strength ~ as.integer(treatment), data = xmp11.01,
          subset = brand == 3, col = 3, type = "b")
    legend(3, 0.9, paste("Brand", 1:3), col = c(4, 2, 3), lty = 1)
    fm1 <- lm(strength ~ brand + treatment, data = xmp11.01)
    anova(fm1)      # compare to table 11.1, page 439

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