An explanation in plain english of the dose-response curves, by the National Institute of General Medical Sciences:
One of the most important principles of pharmacology, and of much of research in general, is a concept called “dose-response.” Just as the term implies, this notion refers to the relationship between some effect—let’s say, lowering of blood pressure—and the amount of a drug. Scientists care a lot about dose-response data because these mathematical relationships signify that a medicine is working according to a specific interaction between different molecules in the body.
Sometimes, it takes years to figure out exactly which molecules are working together, but when testing a potential medicine, researchers must first show that three things are true in an experiment. First, if the drug isn’t there, you don’t get any effect. In our example, that means no change in blood pressure. Second, adding more of the drug (up to a certain point) causes an incremental change in effect (lower blood pressure with more drug). Third, taking the drug away (or masking its action with a molecule that blocks the drug) means there is no effect. Scientists most often plot data from dose-response experiments on a graph. A typical “dose-response curve” demonstrates the effects of what happens (the vertical Y-axis) when more and more drug is added to the experiment (the horizontal X-axis).