Study guides › P/S › Research Methods & Statistics
Study Design & Methods
Every research passage begins with one question: how was this study built? You will learn to tell observational from experimental designs, read cohort and case-control numbers, spot the role of randomization and blinding, and judge qualitative methods and ethics.
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What this chapter covers
- Observational vs Experimental Research. The MCAT first asks whether researchers only watched or actually intervened, because that decides what conclusions are allowed.
- Observational Designs: Cohort, Case-Control & Cross-Sectional. Three observational designs appear again and again. Knowing where each one starts tells you what it can and cannot measure.
- Experimental Design: Variables, Controls, Randomization & Blinding. Most MCAT experiment questions ask you to name a variable, explain a control, or say what randomization and blinding protect against.
- Qualitative Methods, Surveys & Research Ethics. Not every study produces numbers, and every study involving people must follow ethical rules that the MCAT expects you to name.
Key points to know
- Experiment = researcher manipulates the variable and assigns groups
- Random assignment is what allows a causal conclusion
- Cohort: exposure first, then follow forward; gives incidence and RR
- Case-control: outcome first, look back; gives OR; good for rare disease
- IV is manipulated; DV is measured
- Random assignment supports causation; random sampling supports generalization
- Qualitative = themes and meaning; quantitative = numbers and statistics
- Ethnography = immersion; grounded theory = themes come from the data
Try a practice question
What most clearly separates an experiment from an observational study?
- Experiments use larger samples
- Experiments always take place in a laboratory
- Researchers manipulate a variable and assign participants to conditions
- Observational studies never use statistics
Show the answer
C. The defining feature is intervention: the researchers set the independent variable and decide who receives it. Sample size, setting, and statistics can be the same in both kinds of study.
Common questions
What does this chapter cover?
Study Design & Methods covers Observational vs Experimental Research, Observational Designs: Cohort, Case-Control & Cross-Sectional, Experimental Design: Variables, Controls, Randomization & Blinding, Qualitative Methods, Surveys & Research Ethics.
What should I know first?
Experiment = researcher manipulates the variable and assigns groups Random assignment is what allows a causal conclusion Cohort: exposure first, then follow forward; gives incidence and RR
22 original practice questions accompany this chapter in the app. Spaced review brings missed ideas back at the right time; it helps memory but cannot promise you will not miss an idea again.