Introduction If you have chosen to conduct an empirical research project, you will be collecting numerical data, and you will need to analyze that data appropriately, being careful not to draw unwarranted inferences. Or you may be reading research that uses statistics, in which case you need to think critically about whether or not the researchers were justified in making the inferences they did. The purpose of this chapter is to help you understand the principles that define “good” research when numbers are involved. Without a doubt, this is a huge subject and one that cannot be covered in a single book, let alone a chapter. We will try to keep the topic manageable in several ways.