MDM Flashcards
types of experimental knolwedge
anecdotal
observational
tested knowledge
observational studies
treatement effect is immediate
impact must be large
comparisons are grounded in historical memory
larged biased by placebo effect and recall bias
no information about sid effects
Kaplan Meier Curve
survival curves
need to note how many patients are represented at each juncture
percentages represent how many patietns are at risk at each time
hash marks are sensored patients because of some reason
Why isn’t observational and anecdotal success enough?
just because a substance may be noxious, does nto mean that all people exposed to it will have an untoward event
How do we know the outcome is valid?
an outcome is valid when chance and bias are taken into account and deemed to not have a major impact on the result
minimizing chance
randomization balances important variables
the mor variables being examined, the greater the number of people needed to balance the variables
alpha/type I error
probability that a study found a treatment difference when, in truth, no association exsists
a study is statistically significant if the probability of an alpha error is <0.5
beta/Type II error
the probability that a study found no difference in treatment when, in truth, an assciation exists
1-beta = power
power is analogous to sensitivity of a dignaosti ctest
benefit of randomization
more likely to balance unknown and unmeasured confounders
number needed to harm
to calciulate, determine the number of people needed to accrue one dath
if 3.3% die with each person treated, then for one death you would need x people or 1=3.3%*x
possible biases
selection biase (where do patients come from?)
spectrum bias (is the severity of disease reasonable)
blinding bias (do the patients or the assessors of their disease know what treatment they are receiving?)
intention to treat analysis
maintains all of the patietns in each of the groups established with randomization even if the patients do not follow their assigned group’s pathway
a patient in the placebo group can bet active therapy and a patient in the active treatment group can stop medication or intervention
preserves effects of randomization
all subjects should be analyzed in the group that they were randomly assigned
corss-over trial
patients serve as their own controls
makes randomization unnecessary
condition must be chronic and similar in spectrum when treatment is stopped
what to look for in a trial
an outcome that matters
a practical intervention
similar groups
unbiased results
evaluation for chance
if all are present then you may we decide to use the new intervention
