Correlation does not imply causation
[1][2] The idea that "correlation implies causation" is an example of a questionable-cause logical fallacy, in which two events occurring together are taken to have established a cause-and-effect relationship.
As with any logical fallacy, identifying that the reasoning behind an argument is flawed does not necessarily imply that the resulting conclusion is false.
Indeed, in the social sciences where controlled experiments often cannot be used to discern the direction of causation, this fallacy can fuel long-standing scientific arguments.
[7] In other cases, two phenomena can each be a partial cause of the other; consider poverty and lack of education, or procrastination and poor self-esteem.
One making an argument based on these two phenomena must however be careful to avoid the fallacy of circular cause and consequence.
A difficulty often also arises where the third factor, though fundamentally different from A and B, is so closely related to A and/or B as to be confused with them or very difficult to scientifically disentangle from them (see Example 4).
The above example commits the correlation-implies-causation fallacy, as it prematurely concludes that sleeping with one's shoes on causes headache.
A more plausible explanation is that both are caused by a third factor, in this case going to bed drunk, which thereby gives rise to a correlation.
Published in the May 13, 1999, issue of Nature,[9] the study received much coverage at the time in the popular press.
[10] However, a later study at Ohio State University did not find that infants sleeping with the light on caused the development of myopia.
This example fails to recognize the importance of time of year and temperature to ice cream sales.
The increased drowning deaths are simply caused by more exposure to water-based activities, not ice cream.
However, as encountered in many psychological studies, another variable, a "self-consciousness score", is discovered that has a sharper correlation (+.73) with shyness.
For example, social workers might be interested in knowing how child abuse relates to academic performance.
[19] The combination of limited available methodologies with the dismissing correlation fallacy has on occasion been used to counter a scientific finding.
[list 1] Correlation is a valuable type of scientific evidence in fields such as medicine, psychology, and sociology.
It is one of the most abused types of evidence because it is easy and even tempting to come to premature conclusions based upon the preliminary appearance of a correlation.
