The perfect correlation exists when two variables change in exactly equal proportion. It is often further classified into two categories.
A linear positive correlation between two variables is depicted by a positively sloped straight line graph. If the ratio for change between the two variables is constant or fixed, then the 2 variables are said to be linearly correlated.
Correlation is a statistical tool that measures the quantitative relationship between different variables. It studies the degree and intensity of the connection between the two variables. The relationship between two variables is studied with the help of a statistical tool i.e. ‘Correlation’.