Usage
In logic, the technical use of the word "implies" means "to be a sufficient circumstance." This is the meaning intended by statisticians when they say causation is not certain. Indeed, p implies q has the technical meaning of logical implication: if p then q symbolized as p → q. That is "if circumstance p is true, then q necessarily follows." In this sense, it is always correct to say "Correlation does not imply causation."
However, in casual use, the word "imply" loosely means suggests rather than requires. The idea that correlation and causation are connected is certainly true; where there is causation, there is likely to be correlation. Indeed, correlation is used when inferring causation; the important point is that such inferences are not always correct because there are other possibilities, as explained later in this article.
Edward Tufte, in a criticism of the brevity of "correlation does not imply causation," deprecates the use of "is" to relate correlation and causation (as in "Correlation is not causation"), citing its inaccuracy as incomplete. While it is not the case that correlation is causation, simply stating their nonequivalence omits information about their relationship. Tufte suggests that the shortest true statement that can be made about causality and correlation is one of the following:
- "Empirically observed covariation is a necessary but not sufficient condition for causality."
- "Correlation is not causation but it sure is a hint."
Read more about this topic: Correlation Does Not Imply Causation
Famous quotes containing the word usage:
“I am using it [the word ‘perceive’] here in such a way that to say of an object that it is perceived does not entail saying that it exists in any sense at all. And this is a perfectly correct and familiar usage of the word.”
—A.J. (Alfred Jules)
“Girls who put out are tramps. Girls who don’t are ladies. This is, however, a rather archaic usage of the word. Should one of you boys happen upon a girl who doesn’t put out, do not jump to the conclusion that you have found a lady. What you have probably found is a lesbian.”
—Fran Lebowitz (b. 1951)
“...Often the accurate answer to a usage question begins, “It depends.” And what it depends on most often is where you are, who you are, who your listeners or readers are, and what your purpose in speaking or writing is.”
—Kenneth G. Wilson (b. 1923)