This paper defines the terms "hypothesis," "prediction," and "conclusion" and shows how to use the terms correctly in scientific investigations in both the school and science education research contexts. The scientific method, or hypothetico-deductive (HD) approach, is described and it is argued that an understanding of the scientific method, which is about developing explanations for puzzling observations, is critical to an understanding of the nature of science, and that more opportunities need to be provided for school students to use it. Some advice is offered for improving science education research efforts and reports. (Contains 1 table.)