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Toronto Notes 2019 Types of Study Design Public Health and Preventive Medicine PH13 Types of Study Design
Qualitative vs. Quantitative
Table 6. Qualitative vs. Quantitative Study Designs
Qualitative
Often used to generate hypothesis (Why? What does it mean?) “Bottom up” approach
Observation → pattern → tentative hypothesis → theory Sampling approach to obtain representative coverage of ideas ,
concepts, or experiences
Narrative: rich, contextual, and detailed information from a small number of participants
Quantitative
Often tests hypothesis (What? How much/many?) “Top down” approach
Theory → hypothesis → observation → confirmation
Sampling approach to obtain representative coverage of people
in the population
Numeric: frequency, severity, and associations from a large number of participants
Source: Adapted from http://phprimer.afmc.ca
Source:TheAssociationofFacultiesofMedicineofCanadaPublicHealthEducators’Network. AssessingEvidenceandInformation.AFMCPrimeronPopulationHealth.
Quantitative Research Methods
Were exposures assigned by the investigator?
Formulating a Research Question
PICO
Population/Patient Characteristics Intervention/Exposure of Interest Comparison Group or Control Group Outcome that you are trying to prevent or achieve
Yes
Experimental Study Random allocation to groups?
No
Observational Study Testing a hypothesis?
Yes
Randomized Controlled Trial
Figure 8. Quantitative study designs
Source: Adapted from http://phprimer.afmc.ca
No
Non- Randomized Designs
Exposure
Cohort Study
Yes
Analytical Study Sampling based on
Outcome
Case-Control Study
No
Descriptive Study
Neither
Cross-Sectional Study
Observational Study Designs
• observationalstudiesinvolveneitherthemanipulationoftheexposureofinterestnorrandomizationof the study participants
• there are two main subtypes of observational studies: descriptive and analytic studies
Descriptive Studies
• describetheeventsandratesofdiseasewithrespecttoperson,place,andtime;estimatesdisease frequency and time trends
• canbeusedtogenerateanetiologichypothesisandforpolicyplanning
Analytic Studies
• observationalstudiesusedtotestaspecifichypothesis
• includesecologicalstudies,cohortstudies,case-controlstudies,andcross-sectionalstudies
An ecological fallacy is an erroneous conclusion made when extrapolating population level data to explain phenomena occurringinindividuals. Anexampleofan ecological fallacy would be concluding that red wine drinking leads to lower risk of death from CVS disease based on an ecological study showing that countries with a higher rate of red wine consumption have a lower rate of death from CVS causes