Researchers randomly allocated 25 beakers containing minnow larvae to receive one of 25 treatment combinations of 5 levels of zinc and 5 levels of copper.
A data frame with 25 observations on the following 3 variables.
amount of copper received (in ppm)
amount of zinc received (in ppm)
protein in minnow larvae exposed to copper and zinc (mug/larva)
Ramsey, F.L. and Schafer, D.W. (2013). The Statistical Sleuth: A Course in Methods of Data Analysis (3rd ed), Cengage Learning.
Ryan, D.A., Hubert, J.J., Carter, E.M., Sprague, J.B. and Parrott, J. (1992). A Reduced-Rank Multivariate Regression Approach to Aquatic Joint Toxicity Experiments, Biometrics 48(1): 155–162.