Study design Flashcards
what does study design allow researchers to do
test hypotheses
why is study design important
making sure correct and significant answers to research questions are achieved
quantitative
numerical collected data
qualitative
uses collected observation and textual data
as the pyramid of evidence increases so does
rigor, quality, reliability
information becomes
increasingly filtered and evidence based
why is the tip narrow
there are far fewer studies which provide strong evidence
types of study design:
- case report
- case control
- cohort
- RCT
- practice guidelines
- systematic review
- meta analyses
case report
Case report
- Describes and evaluates individual cases, often unique cases of disease or condition
o Unexpected events that may yield useful information
o Cases where one or two subject have unexpected disease or disorders
- Often written as a detailed story
- Lowest level of evidence, but important first line of evidence
- Next step would be a case-control study- determine relationships between relevant variables
positives of case reports
- Identification of new trends or diseases
- Can identify rare side effects to new drugs
negatives of case reports
- Cases may not be generalizable
- Weak evidence and not based on systematic studies
case-control
- Retrospective study
- Observational- no intervention is attempted
- Compares subjects with diseases or outcome of interest with subjects free of disease
- Looks back specific risk factors subjects have/are been exposed
- Determines the relationship between the specific risk factor and disease
- Used to estimate odds
positive of case-control
- Less time needed to conduct study because outcome of interest has already occurred
- Multiple risk factors can be looked at
- Can establish association
negatives of case-control
- Retrospective- relies on memory and data is exposed to recall bias- decreasing quality
- difficult to find suitable control group
- Won’t help find treatment
- Involves a certain ‘guessing’ element
- Doesn’t prove causation
cohort studies
- Prospective study
- Contains one or more cohort (group of people with disease or outcome of interest)
- Evaluates disease, risk factors and outcomes
- As the study goes on, outcome of subjects in the cohorts are measured and specific characteristics are related to the outcome/ disease of interest.
positives of cohort studies
- Subjects can be matched, which limits the influence of confounding variables
- Standardization of criteria is easy
- Cheaper than RCT
negatives of cohort studies
- Cohorts hard to identify due to confounding variable
- No randomisation (imbalances in patients attributes)
- Blinding is hard
- Time consuming
RCTs
- Gives strongest clinical evidence
- Randomly assigns participants into an experimental or control group
- Expected differences in outcome between control and experiment group should be in response to the intervention
- Often used in clinical trials- since helps prove causation
positives of RCTs
- Randomisation takes away population bias
- Easier to blind than observational studies
- Statistical methods= easy to use
negatives of RCTs
- Expensive- time and money
- Study population may not be representative of population as a whole
- Drop outs are common
practice guidelines
- Outlines best current practice to aid healthcare professionals in making evidence based decisions
- Produced by a panel of experts
- Based on extensive review of literature
positives of practice guidelines
+
- Based on published literature
- Supports evidence based decision for clinician
negatives of practice guidelines
- Often outdated
- Not available for niche topics
- Expensive and time taxing
systematic reviews
- Review of all relevant studies on a topic to answer a specific clinical/ health related question
- Summarises findings
- Comes to a combined conclusion
positives of systematic reviews
- Uses all literature (unpublished studies included)
- Cheaper
- Less time consuming than a new study
- Means results from different studies can be generalised
- More reliable and accurate than individual studies
negatives of systematic reviews
- Still time consuming
- Heterogeneity of studies may mean studies cannot be combine
meta-analyses
- Subset of systematic review
- Combines qualitative and quantitative studies giving greater statistical power
- Combines results of papers to produce forest plots
- Establishes statistical significance of studies with conflicting results
- Meta-analyses using RCTs alone would produce the highest-level of evidence
positives of meta-analyses
- Greater statistical power
- Data more relevant to population due to larger/ more varied sample
- Evidence based resource
negatives of meta-analyses
- Time consuming
- Not all studies appropriate for inclusion
- Heterogeneity of study populations
