If there is any change in the value of one variable, the value of the others variable is changed in a fixed proportion, the correlation between them is said to be perfect correlation. It is indicated numerically as +1 and -1.

Perfect Positive Correlation:
            If the values of both the variables are move in same direction with fixed proportion is called perfect positive correlation. It is indicated numerically as +1.

Perfect Negative Correlation:
            If the values of both the variables are move in opposite direction with fixed proportion is called perfect negative correlation. It is indicated numerically as -1.