On this Picostat.com statistics page, you will find information about the npk data set which pertains to Classical N, P, K Factorial Experiment. The npk data set is found in the datasets R package. Try to load the npk data set in R by issuing the following command at the console data("npk"). This may load the data into a variable called npk. If R says the npk data set is not found, you can try installing the package by issuing this command install.packages("datasets") and then attempt to reload the data with library("datasets") followed by data("npk"). Perhaps strangley, if R gives you no output after entering a command, it means the command succeeded. If it succeeded you can see the data by typing npk at the command-line which should display the entire dataset.
If you need to download R, you can go to the R project website. You can download a CSV (comma separated values) version of the npk R data set. The size of this file is about 518 bytes.
Classical N, P, K Factorial Experiment
A classical N, P, K (nitrogen, phosphate, potassium) factorial
experiment on the growth of peas conducted on 6 blocks. Each half of a
fractional factorial design confounding the NPK interaction was used
on 3 of the plots.
npk data frame has 24 rows and 5 columns:
which block (label 1 to 6).
indicator (0/1) for the application of nitrogen.
indicator (0/1) for the application of phosphate.
indicator (0/1) for the application of potassium.
Yield of peas, in pounds/plot (the plots were (1/70) acre).
Imperial College, London, M.Sc. exercise sheet.
Venables, W. N. and Ripley, B. D. (2002)
Modern Applied Statistics with S. Fourth edition. Springer.
options(contrasts = c("contr.sum", "contr.poly"))
npk.aov <- aov(yield ~ block + N*P*K, npk)
options(contrasts = c("contr.treatment", "contr.poly"))
npk.aov1 <- aov(yield ~ block + N + K, data = npk)
se.contrast(npk.aov1, list(N=="0", N=="1"), data = npk)
model.tables(npk.aov1, type = "means", se = TRUE)
Dataset imported from https://www.r-project.org.