Correlation and Causation

Correlation occurs between two variables when a change in one of the variables is reflected by a change in another variable.Positive correlation is when an increase in one variable is accompanied by an increase in the other variable.Negative correlation is when an increase in one variable is accompanied by a decrease in the other variable.Even though the data appears to be linked we can not say that a change in one of the variable causes a change in the other variable. In other words, correlation does not mean causation. It could be a co-incidence or there may be another factor causing the observed effect which is linked to one or both variables. There has to be a causal connection and a causal effect must be demonstrated.