Correlations provide information about the direction two variables have in relation to each other. Direction is represented by the + or – sign.
Correlations also provide information about the strength of the relationship. The farther from zero, the stronger the relationship.
However, correlations DO NOT determine cause and effect! In the two previous examples, it is true that the more ice cream a society consumes, the greater the crime rate and the greater the number of drownings.
The reason: Heat. This third variable effects the other variables – The hotter it is, the more ice cream we eat. The hotter it is, the more swimming we do and the more swimming, the more drownings. The same holds true for murder…the higher the temperature, the more violent crimes are committed. Ice cream does not cause murder!