The structure of a clinical research study affects what can be concluded from its findings. Grimes and Schulz used a simple algorithm to classify research studies. The authors are from Family Health International in Research Triangle Park (Raleigh-Durham), North Carolina.
Did the investigator assign exposure(s)?
Type of Study
yes
experimental
no
observational
If experimental study, was there random allocation of subjects?
Type of Study
yes
randomized controlled
no
nonrandomized controlled
If observational study, is there a comparison (control) group?
Type of Study
yes
analytical
no
descriptive
If analytical study, how are cause and effect evaluated?
Type of Study
people exposed are followed to determine outcome
cohort study
people with outcome are studied to determine previous exposures
case-control study
exposures and outcomes determined at one time point
cross-sectional study
Subtypes of descriptive studies:
(1) case report (a single patient is described)
(2) case series report (two or more patients described)
To read more or access our algorithms and calculators, please log in or register.
