Epiville

Quizzes

Quiz 1, Module Causal

1. Which of the following statements best explains the Mayor's false belief that increasing the stork population would increase the birth rate?

  1. The Mayor implied there was an association between the stork population and the birth rate that was not there.
  2. The Mayor mistakenly thought that 2 factors which are statistically associated (the stork population and the birth rate) must be causally related.
  3. The Mayor neglected to look at the statistical significance of the association. Only if the results were statistically significant could he conclude that a causal relationship exists.
Answer (a) — incorrect: Looking at the figure provided in the article, there is clearly an association between the stork population and the birth rate. His mistake was not in ascribing an association between these two, but rather in speculating on the reason for such an association.
Answer (b) — correct: One of the central tenets of epidemiologic study is that association does not necessarily imply causation - there may be alternate explanations for this association (such that a third factor, in this case the Industrial Revolution, is causing both a decrease in storks and a decrease in the birth rate).
Answer (c) — incorrect: 'Statistical significance' only tells you the probability of observing the data that you observed (or something more extreme) given the hypothesis that there is no association between the exposure and outcome. Statistical significance does not indicate that an association is causal. It is merely concerned with whether an association could be due to chance given sampling variability in your data.