The document discusses the key components of experimental design, including variables and controls. It explains that a scientific experiment has three types of variables: the manipulated variable (MV) that is deliberately changed, the responding variable (RV) that is measured in response to changes in the MV, and controlled variables (CVs) that remain constant. It provides examples of how to write a problem statement identifying the MV and RV, make a testable hypothesis, make observations and analyze results, and ask a new question. The document emphasizes that experiments need controls and must be fair tests by changing one factor at a time while keeping other conditions the same.