Lecture 2:epidemiology study design Flashcards
Where is the strongest method of scientific evidence located in the pyramid ?
At the top
Example: Meta Analysis
Where is the weakest method of scientific evidence located in the pyramid?
Bottom
Example: expert opinion, case series
What is the order of the pyramid of hierarchy of scientific evidence?
Meta analysis Systematic review Randomised controlled trials Cohort studies Case control studies Case series/case reports Background information/ expert opinion
How can validity be described?
Measurement validity
Study validity
Internal validity
External validity
What is measurement validity?
The degree to which a measurement measures what it purports to measure
What is study validity ?
The degree to which the inference draw from a study is warranted
What is internal validity ?
Groups used for comparison are selected and compared in such a manner that observed differences between them in terms of dependent variable under study, apart from sampling error, can be attributed only to the hypothesised effect under investigation
What is external validity ?
Generalisability. A study has good external validity if it can produce unbiased inferences regarding a target population (beyond the study participants)
Factors of descriptive studies ?
No comparison
Bottom of pyramid
Important role in medical sciences
Evidence generated from clinical observation
What is cohort studies?
An observational method in Epidemiology, whereby a population is defined at To and is followed up over a period of time, sometimes over ,any years, and exposures and health outcomes of interest remains recorded
What are synonyms of cohort studies?
Longitudinal studies
Prospective studies
What are the pros of cohort study?
Sufficient large follow up
What are the cons of cohort study ?
- lack of control over the groups within the population
- key exposures of interest may go hand-in-hand with confounding factors
What are case control studies?
Retrospective observational studies, they stariate the END POINT and look BACKWARDS to record historical differences in exposure between two or more groups (I.e. cases)
What are the pros of case-control studies?
Make it possible to study the different exposures that may have lead to rare conditions
Suited for study of rare conditions
Suited for historical well documented exposes
What are cons of case-control studies?
Open to a number of biases
What is a Caveat?
An association between a risk factor and a disease
DOES NOT NECESSARILY INDICARE A CASUAL RELATIONSHIP
What are cross-sectional studies?
Observational method in epidemiology that represent a SNAPSHOT of the health picture in a population at a given point in time
What are the pros of cross sectional studies?
Useful for estimating prevalence within a population
What is the study design temporal direction of cohort study?
From exposure to outcome
What is the study design temporal direction of case-control study?
From outcome to exposure
What are randomised controlled trials?
An experimental method in Epidemiology, where participants wishing a population are randomly allocated to two or more groups called INTERVENTION/EXPERIMENTAL groups/ CONTROL groups
What is usually considered the gold standard in terms of hypothesis testing?
High quality Randomised controlled trials
What are the pros of Randomised controlled trials?
Internal validity : minimises confounding bias
Replicability
External validity: generalisability
More likely to influence practice
What are the cons of Randomised controlled trials?
Coverage bias Participation bias Can’t answer all question types Expensive Context- free
When does Confounding occur?
Confounding occurs when the effects of two associated exposures have not been separated, resulting in the interpretation that the effect is due to one variable rather than the other
What is the consequence of Confounding?
The consequence is that the estimated association is not the same as the true effect
………..study design answer…………types of questions
Different
Different
What is qualitative research?
Any type of research that employs non-numerical information to explore individual or group characteristics, producing findings not arrived at by statistical procedure or other quantitative means (attitudes,acceptability,value,ethics,etc)
What factors must you consider in choosing the appropriate method ?
Outcomes measures: qualitative or quantitative? Valid and reliable? How can they be operationalised?
Duration: over what period of time will outcomes manifest themselves
Controlling variables: how can the effects of extraneous aria let’s be minimised?
What is meta-analysis?
Pooling results in a statistically valid fashion
What is systematic review?
Identifying, quality appraising and synthesising ALL published information in a giving clinical area
All epidemiological studies must be reviewed and approved by ethical review committees
True or false
True
What are the ethical principles that apply to epidemiological practice and research?
Informed consent
Confidentiality
Respect for human rights
Scientific integrity
Epidemiological research methods can be used to answer questions regarding Clinical and Public Health risk factors and interventions.
True or false
True
Randomised Controlled Trials are usually considered the ‘gold standard’, especially for testing interventions, AND they’re not always feasible or ethical
True or false
False
A study of any design is likely to have a range of strengths and weaknesses.
True or false
True
Qualitative methods may be used to gain in-depth data about attitudes, and quantitative data are not normally required for hypothesis testing
True or false
False
