insectCounts {twoway}

Counts of an insect for the combinations of 4 treatments and 6 areas of a field

Description

Counts of numbers of an insect, Leptinotarsa decemlineata (the Colorado potato beetle), each of which is the sum for two plots treated alike, for all combinations of 4 treatments and 6 areas of the field chosen to be relatively homogeneous.

Format

a 4 x 6 matrix, where the rows are treatments and the columns are areas of a field.

Details

These data are used in Tukey (1977) Exhibit 1 of Ch 11 and throughout the chapter as examples of median polish. Because the data are counts, either a sqrt or log transformation would be reasonable.

References

Tukey, J. W. (1977). Exploratory Data Analysis, Reading MA: Addison-Wesley. Exhibit 1 of chapter 111

Examples

insect.2way <- twoway(insectCounts, method="median")
print(insect.2way, digits=2)

plot(insect.2way)
plot(insect.2way, which="diagnose")

# try sqrt transformation
insect.sqrt <- twoway(sqrt(insectCounts), method="median")
print(insect.sqrt, digits=2)

plot(insect.sqrt)
plot(insect.sqrt, which="diagnose")