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Postgraduate Course
5-step approach
EBMgt is a 5-step approach
1. Formulate an answerable question (PICOC)
2. Search for the best available evidence
3. Critically appraise the quality of the found
evidence
4. Integrate the evidence with managerial
expertise and organizational concerns and apply
5. Monitor and evaluate the results
Postgraduate Course
Why are disciplines as such as
psychoanalysis, astrology and
parapsychology widely regarded as
pseudo-science?
Intermezzo
Postgraduate Course
“It is easy to obtain evidence in favor of virtually any theory,
but such ‘corroboration’ should count scientifically only if it
is the positive result of a genuinely ‘risky’ prediction, which
might conceivably have been false.
… A theory is scientific only if it is refutable
by a conceivable event. Every genuine test
of a scientific theory, then, is logically an
attempt to refute or to falsify it.”
Falsifiability
Carl Popper
Postgraduate Course
“Inspect every piece of pseudoscience and you will find a
security blanket, a thumb to suck, a skirt to hold.
What have we to offer in exchange? Uncertainty!
Insecurity!”
Falsifiability
Isaac Asimov
Postgraduate Course
The best available evidence =
Studies with the highest internal validity
Studies with the highest external validity
Postgraduate Course
internal validity = indicates to what extent the
results of the research may be biased and is thus
a comment on the degree to which alternative
explanations for the outcome found are possible
(confounding).
Internal validity
Postgraduate Course
Three criteria:
1. the "cause" and the "effect" are related
2. the "cause" precedes the "effect" in time
3. there are no plausible alternative explanations for the
observed effect
When do we know there is causal relation?
Causality
Postgraduate Course
Considerations for research:
Causality
1. Are the "cause" and the "effect” related: effect size
2. Does the "cause" precedes the "effect" in time:
before and after measurement
3. Are there no plausible alternative explanations for the
observed effect: randomization, control group
INTERNAL VALIDITY
Postgraduate Course
internal validity = indicates to what extent the
results of the research may be biased and is
thus a comment on the degree to which
alternative explanations for the outcome found
are possible (confounding).
Internal validity
Postgraduate Course
Bias: distortion of the outcome due to
systematic errors caused by the way the
study is designed or conducted.
NB: If bias is not taken into account then any
conclusions drawn may be wrong!
Bias
Postgraduate Course
1. Selection bias
2. Information (detection) bias
3. Performance bias
4. Exclusion (attrition) bias
5. Publication bias
…
…
30. …..
Forms of bias
Postgraduate Course
Error in the way participants in a study were selected.
Because of this comparison groups differ in measured or
unmeasured baseline characteristics.
Selection bias
Postgraduate Course
Distortion of the outcome due to misinterpretation of information
or systematic errors in the the measurement of research
variables which leads to misclassification.
Information bias can be prevented by the use of standardized
measurement instruments, hard outcome measures, validated
questionnaires and objective, independent and blinded
assessors.
Types of information bias:
Reporting bias (recall bias)
Observer bias (interviewer bias, halo-effect)
Information bias
Postgraduate Course
Confounding is the idea that a 3rd variable can distort or
confuse (or confound..) a relationship between two other
variables. For instance, when factor X causes disease Y,
that relationship could be confounded by factor C that is
associated with both factor X and disease Y. C would be
an alternative explanation for the relationship observed
between X and Y.
Confounding
Postgraduate Course
What are the confounders?
1. Shoe size & quality of handwriting
2. Body length & body weight
3. Number of storks & birth rate
4. Smoking youngsters & better lung function
Postgraduate Course
Cause and effect can be established
only through the proper research
design: no amount of statistical hand
waving can turn correlations into
conclusions about causation !!!
Internal validity
Postgraduate Course
Levels of internal validity
It is shown that …
It is likely that …
Experts are of the
opinion that …
There are signs
that …
Postgraduate Course
The levels of internal validity can only be used to determine which type of research is the best method to assess the validity of the cause-and-effect relationship that might exist between an intervention (or moderator) and its outcomes. In this respect, cross-sectional studies and case-studies have the ‘weakest’ design. This of course doesn’t mean that cross-sectional studies and case-studies have a weak design overall. After all, different types of research questions require different types of research designs. A case study for instance is clearly a strong design for assessing why or in which way an effect has occurred, but obviously not the most suitable design for assessing the strength of a possible cause-and-effect relationship.
Keep in mind!
Postgraduate Course
But … sometimes observational
studies are as good as RCT’s
Internal validity
When the size of effect is very large (swamps
the bias)
Postgraduate Course
These treatments have not been tested in RCTs: are they supported by poor evidence?
Internal validity
Heimlich manoeuvre Dehydration: drinking water
Cardiac arrest: AED
Postgraduate Course
Ecological validity: Is your organization so different from those in the study that its results may be difficult to apply?
Population validity: Is your population so different from those in the study that its results may be difficult to apply?
External validity: generalizability
Always ask yourself to what extent the evidence is generalizable to your situation:
Postgraduate Course
Generalizability
Same Population?
Same Intervention?
Same Comparison?
Same Outcome?
Same Context?
Postgraduate Course
Generalizability
Keep in mind:
What works in one narrowly defined setting
might not work in another,
but some psychological principles
are generalizable to all human beings.
Postgraduate Course
Internal vs external validity
All research designs are flawed – though each is flawed
differently. For instance, research designs with a high internal
validity, such as controlled studies, may be less suited to
generalization, which restricts their practical usability. Sample
surveys and field research, on the other hand, have lower
internal validity, but can sometimes be more useful for
management practice. So there is always a trade off between
internal validity (precision in control and measurements of
variables) and external validity (generalizability with respect
to populations, setting and context).