Health Science midterm #2
Card Set Information
Health Science midterm #2
Chapter 12 13
Randomized controls trials and causal inference confounding variables
How is the exposure given in Randomized control trials?
the exposure variable
What are experimental studies most commonly used for?
of health care services
how are the volunteers put into the exposed and unexposed group in RCT?
How do you analyze the data in a RCT?
in exposed (treated) and unexposed (untreated)
What is equipoise? (2)
ethical justification of RCT
no convincing evidence that A is better or less toxic than B
In RCT, what is the purpose of random allocation?
Randomization in RCT , reduces ___________ error, nut __________ error may still be present
What kind of bias does randomization reduce?
Ideally, the arm to which the next participant is going to be assigned should be ________.
In randomization, neither the ________ or the __________ should be able to tell any difference
Randomization reduces the chances that groups are different with regard to _________ and _______ risk factors.
What is placebo?
medicine adapted more to please than benefit the patient
What is blinding?
when nobody knows who received what treatments
what is single blind?
only patient blinded
what is double blind?
investigators and patient blinded
what is triple blind?
investigator, patient and statisticians blinded
What are the pros of RCT? (2)
we can infer
reduces allocation bias
what are the cons to RCT? (2)
expensive and non-compliance
inappropriate in certain scenarios
(long latency period between exposure and outcome)
What relationships are RCT best for?
best to test
cause and effect relationship
Koch provided a framework for identifying __________ of infectious disease.
What are Koch's postulates? (3)
The agent has to be
present in every case
of the disease.
agent has to be
the agent has to
cause disease when inoculated
into a susceptive animal and the agent must then be able
to be recovered
from that animal and identified
What are the three reasons that Koch's postulates are useful but not rules?
may require cofactors
like bacteria b/c viruses
need living cells
pathogenic viruses can be
present without a clinical disease
What is Sir Austin Bradford Hill's Causal Considerations? (9)
strength of association
: size of RR
: study replication
: exposure leads to single disease
: exposure precedes disease
: consistent with biology
: natural history of disease
: animal or human
What was the purpose of Hill's causal considerations?
guidelines to help determine
if associations are causal
How is strength of association measured?
, relative risk
How do you know the relationship between X and Y is not due to an extraneous variable?
stronger the relationship
between the independent and dependent variable, the less likely the relationship between X and Y is not due to an extraneous variable
How does consistency increase the credibility of a finding?
, of an association, with
different measurement instruments
increase the credibility of a finding.
How does temporality help with casual consideration?
How does coherence help with the causal considerations?
the association must be coherent with other knowledge
How does specificity help with the causal considerations?
showing that an
outcome is best predicted by one primary factor
odds credibility to a causal claim
How does dose-response relationship help with the causal considerations?
There should be a
direct relationship between the risk factor
and people's status of the disease variable
How does plausibility help with the causal considerations?
A hypothesized relationship
, between exposure and outcome, must
make sense with current biological knowledge.
How does experimental evidence help with the causal considerations?
based on experiments
will make a
causal inference more plausible
What is a cause?
is an event condition or characteristic that
preceded the disease
the disease event would either
not have occurred
at all or would have occurred later on.
What is the three main criteria for a confounding variable?
associated with exposure
risk factor for outcome
does NOT fall along the causal pathway
between exposure and outcome
What is a confounding variable?
between an exposure and an outcome is observed as a result of the
influence of a third variable
Why is it important to consider confounding variables?
it can lead to make invalid conclusions
What is the first step to addressing confounding? (2)
know your subject area
know which variables are likely to confound
the relationship between your primary exposure and outcome
How do you prevent or handle confounding in your research at the design stage? (2)
balance known and unknown confounders by
randomizing your subjects
restrict your study population
to one level of the confounder
How do you prevent or handle confounding in your research at the analysis stage? (2)
multivariable analysis techniques
Confounding occurs when we confuse __________ with _________.