Correlation is a statistical measure of the level of association between two numerical variables. It gives us an idea of how closely two variables are related with each other. For example, age and income are quite closely related variables. It has been observed that the average income grows with age within a threshold. Thus, we can assume that age and income are positively correlated with each other.
Note
However, correlation does not establish a cause-effect relationship. A cause-effect relationship means that one variable is causing a change in another variable.
The most common metric used to compute this association is the Pearson Product-Moment Correlation, commonly known as Pearson correlation coefficient or simply as the correlation coefficient. It is named after its inventor, Karl Pearson.
The Pearson correlation coefficient is computed by dividing the covariance of the two variables by the product of their standard deviations. The correlation value lies between -1 and +1...