The following are all examples of real-life stories about vasovagal symptoms during bowel movements: The bad part is that, with the rectal pain, I will begin to have a vagus response: my throat will tighten, I will begin salivating, get hot and sweaty.
Confounding occurs when the experimental controls do not allow the experimenter to reasonably eliminate plausible alternative explanations for an observed relationship between independent and dependent variables. Consider this example.
In this article, we (a) explain what extraneous variables are, providing some examples, (b) highlight when extraneous variables become confounding variables, as well as how extraneous and confounding variables can be a threat to internal validity; and (c) explain how to deal with extraneous variables in your research.