This block requires you to identify and differentiate between some of the common study design types. Before we start, just know that it's not always possible to categorize every study neatly into a study design type. Some studies are a combination of two or more study design types. Nevertheless, for the sake of the block exam, you have to try your best to identify what sort of study design a study is just based on the title.
When faced with a study title, follow these steps to identify the research design type:
- Exclude qualitative studies. First, differentiate quantitative from qualitative. Qualitative research asks a very open-ended and broad question and is able to accept a wide variety of answers. Qualitative research often asks questions about what people say, what people actually do, and what people actually believe. Keep in mind that qualitative research has no variables, statistical analysis, and often no control either.
- Exclude experimental studies. This is easy. Just look for the words "randomized" (and sometimes "non-randomized") and "trial".
- Exclude descriptive studies. Now we're left with observational studies: analytical and descriptive. Analytical study titles include the words "greater than, less than, causes, leads to, compared with, more likely than, associated with, related to, similar to, or correlated with". Everything else is descriptive. Also, descriptive studies don't have a control group.
- Exclude cross-sectional studies. Now that descriptive studies have been excluded and we're left with analytical studies, we have to carefully differentiate the different types of analytical studies: the easiest to exclude at this point are cross-sectional studies. Remember, cross-sectional studies are about right now - they do not collect data over time, so they're always about prevalence (not incidence!) and about correlation (rather than causality).
- Exclude case-control studies. Now we're left with case-control and cohort. Case-control takes people that already have a disease (and a control group of those that don't) and tries to see which exposures are more common in each group to try to discover a possible causality.
- Cohort studies
PICO and FINER
- "P" Population of interest
- Patient or the problem to be addressed
- "I" Intervention
- Exposure to be considered–treatments/ tests
- "C" Control
- Control or comparison intervention treatment/placebo/standard of care
- "O" Outcome
- Outcome of interest
- "F" Feasibility
- Sufficient resources in terms of time, staff, and funding. Use of appropriate study design. Manageable in scope. Adequate sample size. Trained research staff.
- "I" Interesting
- Interesting as a researcher or collaborator. Investigator’s motivation to make it interesting.
- "N" Novel
- Thorough literature search. New findings or extension of previous findings Guidance from mentors and experts.
- "E" Ethical
- Following ethical guidelines. Regulatory approval from Institutional Review Board.
- "R" Relevant
- Influence on clinical practice. Furthering research and health policy.
Levels of Subject Selection
- Developing a research question on NCBI.
- Understanding Research Study Designs
- Research designs (Slides) on Slideplayer.com.
- Distinguishing case series from cohort studies
- Observational research methods: cohort, cross sectional, and case-control studies on BMJ.com.