There are many studies that exist that show that two variables are related to one another. The strength of a relationship between two variables is called correlation. Variables that are strongly relat...There are many studies that exist that show that two variables are related to one another. The strength of a relationship between two variables is called correlation. Variables that are strongly related to each other have strong correlation. However, if two variables are correlated it does not mean that one variable caused the other variable to occur.