Linear correlation analysis is a statistical technique use in the measurement of causation, direction, degree and significance of co-variation between two or more variables. The conclusion cigarettes cause the pulse rate to increase isn’t valid because linear correlation tells us the strength of the relationship, and does not imply a casual relation. A casual relation says that if one variable increases it causes to increase the other variable as an effect. It means that we cannot say which variable is the cause if there is a significant linear correlation exists between the two variables. Linear correlation always depicts the strength of the relationship between two variable s but it never depicts the casual relationship between two variables.