A research design is a plan for answering a research question, a plan for testing the hypothesis. Psychology researchers typically rely on four main types of research designs: observational and correlational, experimental, quasi-experimental, and single-case designs. The design researchers choose depends on the research question and hypothesis, and ultimately, their goal for the research. In this section, we will cover each research design and provide examples. As you'll see, this section provides more details than other sections. This is because choosing the research design is one of the most important steps in the research process.

What research design should I choose if I want to describe or predict people's behavior?

• How do I conduct an observational or correlational study?
• Can a study be both observational and correlational?

What research design should I choose if I want to understand the causes of behavior?

• How do I "control" a variable?
• How do I know whether the variable has an effect?
• Apology-present Condition
• No-apology Condition
• How do I conduct an experimental research design?
• Should people participate in all conditions of my experiment?
• Because different people participate in each condition, could this explain any differences in the outcome?
• Isn't it possible that conditions of an experiment differ in other ways, besides the independent variable?

What research design should I choose if I want to understand the causes of behavior or create change in the "real world"?

• How do quasi-experiments differ from "true" experiments'?
• How do I conduct a quasi-experiment?

What research design should I use if I want to understand and treat the behavior of one person?

• How do I conduct a single-case research design?
• Can I make a claim that a treatment causes a client to improve?