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.
Correlation is a statistical measure (expressed as a number) that describes the size and direction of a relationship between two or more variables. A correlation between variables, however, does not automatically mean that the change in one variable is the cause of the change in the values of the other variable. Causation indicates that one event is the result of the occurrence of the other event; i.e. there is a causal relationship between the two events.