Why learn how to analyze data by examining the relationships between quantitative data?

Often multiple pieces of data are gathered on a single subject or data from two different data sets can be paired together. When the variables involved are quantitative variables, we want to know if there is a relationship between the two variables. For example, is there a relationship between the third exam score for students in a math class and their final exam score? And if there is a relationship, how can we predict a particular student’s final exam score from their third exam score? Scatterplots and lines of best fit can be used to answer these questions. The scatterplot below shows a positive linear relationship between the third exam score and the final exam score for the data.