For the ones below, we aren't going to talk about them much, you learn about them in advanced statistics classes. Mainly what I want you to know is that we have statistical techniques available for (A) dealing with the third variable problem - if we measure the third variables, we can control for them and see if there is still a relationship between X and Y, and (B) we can build statistical models that connect many variables together - we aren't limited to just two variables. Partial correlations A