The Science Buddies website aims to promote deep understanding of scientific research through student science fair projects. This segment of the website provides explicit help in understanding variables and designing a fair test. The page includes: 1) Background information: What are variables in scientific inquiry and why is it important to identify them? 2) Eight short examples of scientific questions with independent and dependent variables identified. 3) Sample write-up of a simple experiment with hypothesis, experimental groups described, and variables to be controlled 4) Student checklist for selecting good variables