We must be careful when interpreting the meaning of association. Although two variables may be associated, this association does not imply that variation in the independent variable is a cause of variation in the dependent variable (or vice versa). For instance, age and income are usually related. However, a mere increase in age does not cause an increase in income. We can determine the presence or absence of association through statistics. However, there is no basis for concluding that a cause-effect relation exists between these variables.