Graziano & Raulin
Research Methods (9th edition)
Identifying and Controlling
Confounding Variables
Although it is theoretically possible for a researcher to be able to identify every possible confounding variable by thinking through the problem extensively, it is rarely possible to do that in practice. Researchers rely on a combination of their own analysis of the possible sources of confounding and a review of what other scientists have learned about sources of confounding from previous research.
Take the issues that you investigated in setting up research hypotheses and conduct a detailed analysis of the potential sources of confounding. Brainstorm on how you might control each of the various sources of confounding. In Chapter 9, you will learn about systematic control procedures that can be applied, but most of those procedures are only logical steps for the controlling of confounding that has been identified. Give it a shot. We bet you will surprise yourself with what you can come up with.
If you want a little help on how to spot confounding variables in a study, check out the tutorial elsewhere on this website.