Sometimes you want to analyze relationships between sets of data. For example, imagine that you are a factory manager. You wish to know if the production speeds of the cars on your production line relate to the quality issues. When speed is higher, do quality errors also tend to be high? When speed is lower, do errors also tend to be low?

This chapter covers only the basic starting blocks of associating variables. Some chapters later in the book give some slightly more advanced examples. Ultimately, there are many more complex methods not covered in this introductory book.