3 - Study designs (part I): Observational epidemiological studies Flashcards
What is a target population?
the whole group you want to study
What is a study population?
one where you can legitimately apply your conclusions of the study
systematic sampling
Every nth item in the target population is selected
- Not useful if there is a pattern in your list
stratified sampling
- Divide population into sub-groups and and take sample from there
census
all the population
sample
fraction of the population
types of non-probabilistic sampling
- convenience
- purposive
- quota
- snowball
types of probabilistic sampling
- simple random
- systematic
- stratified
- complex
experimental study
investigator controls which subjects receive the treatment/ exposure under consideration
observational study
investigator does not control which subjects receive treatment/ exposure under consideration
types of observational studies
descriptive and analytical
what are the types of descriptive study
- case report
- case series
what is a case report
- individual based measurements
- prevalence studies
What is a case series?
A written report on the details of a cluster of related cases
what are the types of analytical study?
- case-control
- cohort
- cross sectional
- ecological study
- systemic review
- meta-analysis
what are the reasons for carrying out an observational study?
- cheap
- quick
- ethical reasons
- wide range of diseases can be investigated
cross-sectional study
A study in which a representative cross section of the population is tested or surveyed at one specific time.
Case-control study
- used to identify factors that may contribute to a medical condition
- compares a group of patients who have that condition with a group of patients who do not.
cohort study
a group of exposed individuals (individuals who have been exposed to the potential risk factor) and a group of non-exposed individuals are followed over time to determine the incidence of disease
case-control study vs cohort study
Case-control - Retrospective only, (Looking for risk factor exposure in pts with known outcomes)
Cohort - can be prospective or retrospective (Looking for outcomes in patients with predefined exposure to risk factor or disease state)
Nested case-control study
- case control-study
- cases and controls are drawn from the population in a cohort study
family studies
Scientific studies in which researchers assess hereditary influence by examining blood relatives to see how much they resemble each other on a specific trait.
ecological studies
Studies that examine mean outcome and mean exposure at an area (and population) level
- however association does not mean causation
systematic review
- review of a clearly formulated question
- uses explicit, systematic methods
- identify, select, and critically appraise relevant research,
meta-analysis
a procedure for statistically combining the results of many different research studies
