Mediators and Moderators, Confounders and Covarites
If you want to have a good belly laugh, I recommend searching the web for "comical causation vs correlation relationships." Among the spurious correlations that I found funniest were "each day in the US, over 6000 people exposed to tap water will die," or "as sunscreen use increases, the number of shark attacks goes up," or "as the use of indoor air-conditioning has increased worldwide, global temperatures have risen." So, the old adage "relationships are tricky" applies to situations far beyond the interpersonal. And it's because relationships are so tricky that statistical tests never "prove" that a relationship exists; instead by rejecting the null hypothesis, statistics merely quantify the probability that no relationship exists.
Read the full editorial in this issue.
Edelle Field-Fote, PT, PhD, FAPTA