An investigatory project is a project that tries to find the answer to a question by using the scientific method. According to About.com, science-fair projects are usually investigatory projects.
An investigatory project starts with a hypothesis, or question, to investigate. For example, "Do plants grow in the dark?" and "Do pet mice learn quicker when given food rewards?" are sample hypotheses. Then the investigator sets up an experiment with two parts. In one part, the hypothesis condition is present, and in the other part, known as the control, the hypothesis condition is not present. For example, to investigate if plants grow in the dark, one plant is placed in the dark and the other in the light.