Study Design Flashcards
What is design of a study based on?
Identification or grouping of subjects
Time course of investigation
Explain how identification of subjects is relevant to study design
E.g. exposed vs non-exposed
or difference in outcomes e.g. cases vs controls
Explain how time course of investigation is relevant to study outcome
E.g. prospective or retrospective
or cross-sectional where exposure and outcome are measured together
Name some descriptive studies
Case report/series
Cross sectional studies
Name some analytical studies
Case-control studies
Cohort studies
Ecological studies
Name some experimental studies
Controlled trials
Uncontrolled trials
What happens in prospective studies?
Subjects exposed to a risk factor or invention are assembled and researcher awaits outcome
What happens in retrospective studies?
Group of individuals assembled because they have already experienced the exposure
Aim of descriptive studies
Describe characteristics of a group of subjects
What does not happen in descriptive studies compared to other studies?
No testing of causal hypothesis
No comparison with other groups
What can cross-sectional studies do that case reports/series cannot?
Suggest presence of putative relationship among variables
Another name for cross-sectional studies?
Prevalence studies - describe various attributes of subjects at a single point in time
What type of studies are surveys?
Cross-sectional
What type of studies are census?
Cross-sectional
What happens in prospective longitudinal studies?
Observations are repeated in same population over long period of time
What are prospective longitudinal studies helpful for?
Studying natural course of illness, risk factors and incidence rates
Disadvantages of longitudinal studies
Costly
Time consuming
What are analytical studies?
Comparative analysis of two groups to measure association between variables of interest
Populations that can be studied in cross-sectional studies
Exposed and diseased
Exposed but no disease
Not exposed but diseased
Not exposed and no disease
What happens in a case-control study?
Researcher assembles group of subjects who have experienced the outcome - cases and who have not - controls
Researcher estimates proportion in each group who have experienced exposure.
When is hypothesis of case control study supported?
If proportion of exposed subjects is larger among case group than control group
What is a cohort study?
Observational study of a group of people with specific characteristics of exposure who are followed up to detect an outcome
What type of study is an ecological study?
Analytical
What happens in an ecological study?
Data is gathered to describe what happens in a group rather than an individual
What is the unit of measurement in an ecological study?
Population
What is the assumption underlying ecological studies
All members of a given population are equally exposed and carry same risk of disease
Problem of ecological studies
Tells us nothing about the individual
Does not note individual differences and risk factors
What is ecological fallacy?
Drawing individual conclusions based on group-level observations in ecological studies
What happens in experimental studies?
Exposure is experimentally assigned to groups in variable fashion to observe effect
How are experimental studies different to cohort studies?
Deliberate manipulation of exposure (i.e. intervention)
What type of study is a clinical trial?
Experimental
What is another name for experimental studies?
Interventional
What questions does a cross-sectional study ask?
How common is a condition?
What is the nature of this sample?
What questions does a case-control study ask?
What are the causes of this outcome?
What questions do interventional studies ask?
What is the effect of this intervention?
What questions do cohort studies ask?
What are the effects of this risk factor/exposure?
Best study to enquire treatment effectiveness?
Pragmatic RCT
Systematic review
Best study to enquire treatment efficacy
Experimental RCT
Systematic Review
Best study to enquire causation/aetiology?
Cohort
Case-control
Best study to enquire prognosis?
Cohort
Best study to enquire diagnostic assessment (new tool)?
Cross-sectional comparison to gold standard
Best study to enquire health economics?
Cost-effectiveness study
Best study to enquire ‘meaning’ or health ‘experience’
Qualitative study
