Friday, April 4, 2014

Gather more evidence before you draw conclusions: The Correlation Equals Causation Fallacy

The correlation equals causation fallacy is very common both in everyday usage and in formal arguments, and it occurs when someone confuses “correlation” (when things occur at the same time or immediately after one another) with “causation” (when one thing causes another). It is a mistake to assume that the order of events means that one event caused the other. There are many other variables that could contribute to the pattern we see including pure coincidence or, most frequently, a common “third” cause of both events. Statistics play an important role in this fallacy. Many will see a figure and automatically draw a conclusion without thinking of what may have been left out. This is why it is important to examine the test conditions for an experiment and all other available data. However, if one dismisses valid statistical conclusions based on this fallacy, they are committing another fallacy: “denial of causation.”(Other names of this fallacy include the false cause, post hoc, faulty causality, correlation vs. causation, and post hoc ergo propter hoc).

How it applies: This fallacy is often used in trying to convince someone that to accept evolution you must also reject God because because scientists are less likely to be religiously active than the general public. However, by nature, scientists tend to think logically and analytically and prefer objective data over other types of knowledge. Therefore, people who would be attracted to the sciences might also doubt the existence of a supernatural being. One does not necessarily cause the other as there are many religious scientists.


  • In the 1990’s, religious attendance and illegal drug use both rose. Therefore, religious attendance caused illegal drug use. (Alternative: Illegal drug use resulted in more people feeling the need to attend church or that both rose due to an increase in societal unrest.)
  • A black cat crossed Babbs' path yesterday and, sure enough, she was involved in an automobile accident later that same afternoon. (Also anecdotal fallacy).
  • Drinkers are more likely than non-drinkers to get lung cancer, suggesting drinking causes lung cancer. (Alternative: people who drink more also tend to smoke, or smoke more, than non drinkers.)
  • Many claim that marijuana is a “gateway drug” because those who have smoked marijuana are more likely than those who haven’t to go on to try other drugs. (Alternative: those who are willing to try one drug are obviously also willing to try other drugs.)
  • Global warming has increased as the number of pirates has decreased. This is because the pirates are the original “Pastafarians” and are “absolute divine beings,” and, due to our disrespect of them, the Flying Spaghetti Monster is punishing us.
  • There is a strong correlation between the number of serious crimes committed and the amount of ice cream sold by street vendors. Therefore, criminals love ice cream. (Alternative: both increase with temperature).
  • Mortality rates decrease with the number of televisions per capita. Therefore, TVs will keep people from dying (Alternative: both are due to gross domestic product).

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