Correlation Between a Pair of Data
First step in examining bivariate data is to identify some type of association between the values of two variables. Such relationship is called correlation. Correlation between the values of two variables is a measure to show how much the variables are related to each other.
For example, in the graph below, you notice that as the values of x variable increases the value of y variable increases as well. This indicates that there is some type of correlation between values of x variable and the values of y variable.