Different research designs answer different questions. Educators cannot use nonexperimental quantitative research designs, such as descriptive surveys and correlational research, to determine definitively that an intervention causes improved student outcomes and is an evidence-based practice. However, such research can (a) inform educators about a number of issues related to the education of students with disabilities and (b) guide experimental research efforts that can more definitively determine whether a practice is evidence based. Additionally, in the absence of relevant, high-quality experimental research, special educators can use some types of correlational research as the best available evidence to guide their instructional and curricular decision making. (Contains 1 table.)