Correlation is not causation!

Anyone who has taken an intro to psych or a statistics class has heard the old adage, "correlation does not imply causation." Just because two trends seem to fluctuate in tandem, this rule posits, that doesn’t prove that they are meaningfully related to one another.

Correlation is a statistical measure that describes the size and direction of a relationship between two or more variables. 

Causation indicates that one event is the result of the occurrence of the other event; i.e. there is a causal relationship between the two events. 

Causality is the area of statistics that is commonly misunderstood and misused by people in the mistaken belief that because the data shows a correlation that there is necessarily an underlying causal relationship.

A good example is that the rate of drowning on Sydney’s beaches is positively correlated to the sale of ice cream.

An incorrect conclusion is that “the consumption of ice cream leads to drowning”. More likely the reason would be that both drowning and ice cream sales are positively affected by hot weather; more people are at the beach and more ice creams are sold- correlation does not imply causation!.

A few examples from recent articles and headlines:

“Spiritual people are more likely to be mentally ill” -The Daily Mail 

 “...children whose parents smoked were more likely to exhibit delinquent behaviour”- The Guardian

“People who have large weddings are less likely to get divorced”- Psychology Today

“Men and women who eat more of the sweets are also likely to be depressed”-LA times

“Coffee may prevent depression, scientists say”-BBC

Don’t be duped by Facebook trends- correlation does not imply causation