In statistics the phrase “correlation does not imply causation” refers to the inability to legitimately deduce a cause-and-effect relationship between two variables solely on the basis of an observed association or correlation between them.

Two events occurring together are taken to have established a cause-and-effect relationship. This fallacy is also known by the Latin phrase cum hoc ergo propter hoc (‘with this, therefore because of this’).

Very often we are victim of this bias.

Correlation between Ice cream sales and sunglasses sold is very strong statistically.

As the sales of ice creams is increasing so do the sales of sunglasses.

Some hidden factors can be the cause. In this example the weather is the hidden factor which is causing both the things.

The same strong association exists among yellow-stained finger and lung cancer.

Some hidden factors can the cause of both the things. In this example is the tobacco smoking.