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.
The use of random allocation and the elimination of allocation bias meant that treatment groups would be similar in baseline characteristics, thereby minimising confounding. Confounding is a difference between treatment groups in the characteristics that influence the association between the treatments and outcomes.