Correlation

Correlation is defined by dict.org as:

a statistical relation between two or more variables such that systematic changes in the value of one variable are accompanied by systematic changes in the other [1]

In other words, if you are studying two

Correlation and causation

A correlation between two variables does not always mean that one variable has caused a change in the other. Often a third variable is causing both, such as shark attacks and ice cream sales. These two factors may correlate, but they are not directly related. Rather, both go up each summer as people go swimming at ocean beaches.

It is a logical fallacy to assume that correlation implies causation.

The following is a flawed argument:

1. Event A occurs in concurrence with Event B
2. Therefore, Event A causes Event B

This is flawed because:

1. There may be a confounding factor causing A and B
2. B may cause A
3. The relationship may be a complete coincidence

Examples

1. As sales of ice cream rise, so do reports of shark attacks
2. High sales of ice cream cause shark attacks

Flaw: Shark attacks and ice cream sales follow a seasonal pattern. Both rise in the summer months. The seasons are a confounding variable.

1. Since the construction of a stadium began in Alaska, the value of your home in Texas has risen
2. Stadium construction in Alaska causes higher home values in Texas

Flaw: This is a coincidence between unrelated variables.

References

• Texas A&M University