1. Ignoring a covariate: An example of Simpson's paradox.;Appleton;American Statistician,1996
2. Smoking and lung cancer: Recent evidence and a discussion of some questions.;Cornfield;Journal of the National Cancer Institute,1959
3. Simpson's paradox and the analysis of memory retrieval.;Hintzman;Psychological Review,1980
4. Random sampling, randomization, and equivalence of contrasted groups in psychotherapy outcome research.;Hsu;Journal of Consulting and Clinical Psychology,1989
5. Statistical principles for clinical trials. International Conference on Harmonisation E9 Expert Working Group.;Statistics in Medicine,1999