Purity of product from a filtration process
A data frame with 12 observations on the following 4 variables.
indicator factor for technician
a factor with 3 levels
a factor with 2 levels
a response factor
This experiment was run by two technicians to study the impact of two process factors on the purity of the product after filtration.
Peter R. Nelson, Marie Coffin and Karen A. F. Copeland (2003), Introductory Statistics for Engineering Experimentation, Elsevier. (Appendix A)