Study designs Flashcards
2 components of study design
Population:from which groups of subjects are studied
Outcomes:that are measured
components of analytic studies
1.intervention
2.exposure
spotting the design:
what is the 2 aims of the study?
1.describe population(descriptive)
2.qauntify the relationship between factors (analytical)-PICO questions
spotting the design, step 2:
1.yes(RCT)
2.No(observational)
spotting the design step 3:
-period after exposure or intervention-cohort study
-same time as exposure or intervention-cross-sectional analytical study
-before the exposure was determined-case control study
Descriptive studies
-describe patterns of disease occurrence in relation to variables such as person, place and time
-first step into a new topic-event, disease and or condition
what are the 2 aims for descriptive disease
- emphasis features of a new condition
- describe the health status of communities or populations
descriptive question include 5 W
what, where, why, who when
descriptive study(what)
condition or disease being studied?
-magnitude of problem, prevalence of disease or health-related event
descriptive study-why, can a descriptive study confirm causative/ risk factors?
no
3 examples of individual studies
1.case report
2.case series
3.cross sectional study
example of population level
correlational/ecological study
correlation/ecological studies advantage
use available data-quick and inexpensive
2 Limitations of correlation/ecological studies
1.the degree of association does not reflect an individual-level relationship
2.changes associated with exposure can be masked
3 features of an analytical studies
1.carried out to find the answer to why
2.test hypothesis
3.has a comparison group
-study group
-control group
first step of case control design
1.start with disease(cases)
control group:those without disease
-both groups should be at same risk of being exposed to the factor of interest
3 case control studies advantages
quick and inexpensive
useful to investigate rare disease
minimal ethical issues
3 disadvantages of case control studies
1.recall bias :has to depend on memory or past records to determine exposure
2.difficult to select an appropriate control group
3.cannot measure the incidence
what happens in a cohort study?
investigator selects a group of exposed individuals and group of non-exposed and follows up both groups to compare the incidence of disease
2 types of cohort studies
1.prospective cohort
2.retrospective (historical)
2 types of experimental studies
1.clinical trials-on patients with disease e.g immunisation trial
2.prevention trials-on healthy people/ people at risk of certain conditions e.g community trial