study design Flashcards
what are the steps involved in evidence based medicine
asking focused questions finding the evidence critical appraisal making a decision evaluating performance
what is a stucture used to ask specific questions when evaluating healthcare
PICO
Population
Intervention
Comparator
Outcome
describe the hierarchy of evidence in studies
Hierarchy 1a (level A) Systematic reviews or meta analysis of randomised controlled trials *gold standard*
Hierarchy 1b (level A) At least 1 randomised controlled trial
Hierarchy 2a
At least 1 controlled trial without randomisation
Hierarchy 2b
At least 1 other type of quasi-experimental study
what is the purpose of a critical appraisal
to assess and consider validity, reliability and applicability.
It should be done so that you can apply results to your own patients, provide your patient’s the best possible evidence when communicating risk and to remain professional.
what is validity
Validity is defined as the extent to which a concept is accurately measured in a quantitative study.
what is reliability?
how consistent results are. If the experiment was repeated again, would the same/similar results be seen?
what is applicability
is how relevant a study is to clinical medicine.
what are good qualities of a study
Have random allocation of participants to interventions (reduces bias/confounding variables)
Have outcome measures for at least 80% of participants
Show causation rather than association
what are the categories of observational studies?
descriptive
descriptive and analytical
analytical
name types of descriptive studies?
case reports or series
ecological studies
what are ecological studies, what do they show?
Use routinely collected data to show trends in data and thus is useful for generating hypotheses.
Shows prevalence and association, cannot show causation.
describe what a cross sectional study is
find associations at that point in time by seeing who has /hasnt got the disease
They are used to generate hypotheses
what are the limitations of a cross sectional study
but are prone to bias and have no time reference.
what are case control studies
These are retrospective studies that take people with a disease and match them to people without the disease for age/sex/habitat/class etc and study previous exposure to the agent in question.
what are the benefits of a case control study
It is quick and inexpensive
what are the limitations of a case control study
Retrospective:
shows only associations
data may not be reliable due to problems with patient’s memories.
what are cohort studies
Studies a population over time to see whether they are exposed or not and the consequences of that
what are the advantages of a cohort study
possible to distinguish preceding causes from concurrent associated factors.
There is a lower chance of bias
absolute, relative and attributable risks can be determined.
as its perspective causation can be determined
what are the disadvantages of a cohort study
Requires controls to establish causation.
what type of study is a RCT
experimental/interventional
what are the pros of a RCT
shows causation
bias and confounding factors are limited
what are the cons of a RCT
expensive and have volunteer bias
what are the cons of a non randomised trial
extremely Bias
what is an independent variable
a variable that stands alone and isn’t changed by the other variables you are trying to measure. For example, someone’s age might be an independent variable
what is a dependant variable
a variable that is dependent on the independent variables
what criteria should be evaluated when establishing causality
Consistency Strength of association Specificity (single cause for a single effect) Dose-response relationship Temporal relationship Biological plausibility Coherence with existing theories Altered by experimentation
in terms of independent variable (IV) and dependant variable (DV), describe the different types of causes
Where the IV is necessary for the DV
Where exposure to the IV is sufficient to cause the DV
Where the IV contributes to the DV.
what is a systematic review
A review of a clearly formulated question that uses symptomatic and explicit methods to identify, select and critically appraise relevant research, and to collect and analyse data from the studies that are included in the review.
what is a meta analysis
where statistical methods may be used to analyse and summarise the results of the included studies.
how can meta analysis results be shown graphically
It can be graphically represented as a forest plot.
define qualitative research
Qualitative research involves collecting and analyzing non-numerical data to understand concepts, opinions or experiences.
define quantitive research
Quantitative research means collecting and analyzing numerical data to describe characteristics, find correlations, or test hypotheses.
what are the types of qualitative research
Ethnography
Interviews
Documentary or thematic analysis
define ethnography
emerging oneself in a particular lifestyle or group
what are the problems associated with qualitative data
Interactive kinds: over-analysis of oneself using existing theories
Meaning imposition: not truly understanding what someone else is thinking
Crisis of representation: research cannot capture lived experiences
Reflexivity: personal interpretations of data
Generalisation
