Does a correlation between two variables imply a cause and effect relationship?
No. It is possible that one of the variables causes the other, but without more information it is impossible to tell which variable causes which, or if there is a third variable related to both that is responsible. For example, there is a high correlation between shoe size and reading ability in children. However, it would obviously be silly to say that big feet cause reading ability, or above average reading ability leads to big feet. Clearly a third variable, age, causes increases in shoe size and reading ability.
