When you conduct research, at the end of the data collection phase you will have a data set of some kind. This data set contains the measurements of each research unit on each variable measured and can be used in a number of ways in your research. You may use this data set to statistically test hypotheses that a theory makes about what you should find in your research. Or you may examine the data without any specific theory in mind, just to see what the data tell you about what you are studying. Ultimately, this process requires at some level the description of your data. The data set is largely a disorganized batch of numbers with no obvious meaning or interpretation. In this chapter, I describe various statistical and graphical approaches to summarizing measurements on a variable and discuss how to quantify the direction and strength of the relationship between two quantitative variables.