selection, experimental mortality, and selection-history interactions. One way to minimize the influence of artifacts is to use a pretest-posttest control group design. Within this design, "groups of people who are initially equivalent (at the pretest phase) are randomly assigned to receive the experimental treatment or a control condition and then assessed again after this differential experience (posttest phase)". Thus, any effects of artifacts are (ideally) equally distributed in participants in both the treatment and control conditions. See also References Further reading External links Tutorial: Confounding and Effect Measure Modification (Boston University School of Public Health) Linear Regression (Yale University) Tutorial by University of New England Analysis of variance Causal inference Design of experiments