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Biostatistics
Core I
36
Medical
Graduate
08/27/2011

Additional Medical Flashcards

 


 

Cards

Term
Skewed Right
Definition
Positive Skew - tail to the right
Mean > median
Term
Skewed Left
Definition
Negative Skew - tail to the left
Mean < median
Term
Standard Deviation
Definition
√((x1 - xmean)2.../(n-1))
Term
Standard Error
Definition
s/√(n)
Term
Prevalence
Definition
total cases of dx at time t /
total # of at risk individuals in population
Term
Cumulative Incidence (CI)
Definition
# of New cases of dx over a time period/
Population at risk over time period
Term
Incidence rate
Definition
# of new cases of dx over a time period/
Sum of each persons’ time at risk (person-time) over time period
Term
CI vs IR
Definition
CI = IR * time
only if IR is constant over time period
Term
Case fatality rate
Definition
# deaths due to disease/
# cases of disease
Term
Mortality rate
Definition
# of deaths over time period/
total person-time in time period
Term
Proportional mortality
Definition
# deaths from disease in a population
total # of deaths from all reasons
Term
Proportional mortality
Definition
# deaths from disease in a population
total # of deaths from all reasons
Term
Crude rate
Definition
doesn't account for age or population
Term
Age-adjusted rates
Definition
crude rate * standard population = expected # of events for each population
Term
Risk & Rate difference
Definition
Risk Diff = Cumulative incidence (exposed) – cumulative incidence (non-exposed)
Rate diff = Incidence rate (exposed) – incidence rate (non-exposed)
Term
Relative risk
Definition
Cumulative incidence (exposed)/
Cumulative incidence (non-exposed)
Term
Rate ratio
Definition
Incidence rate (exposed)/
Incidence rate (non-exposed)
Term
Odds ratio
Definition
Odds of being exposed (among diseased)/
Odds of being exposed (non-diseased)
Term
Attributable Risk
Definition
IR(exposed) - IR(non-exposed)
Term
Attributable Risk %
Definition
IR(exposed) - IR (non-exposed)/
IR(exposed) (x100)
Term
# needed to treat (NNT)
Definition
1/absolute risk reduction
Term
Population attributable risk
Definition
IR(pop) - IR(non-exposed)
Term
Population attributable risk %
Definition
IR(pop) - IR(non-exposed)/
IR(pop) (x100)
Term
Case Report Study/series
pros & cons
Definition
Pros: cheap, can ID rare / new diseases - early warning
Cons: no comparison, small n, could be exception
Term
Ecological studies
pros & cons
Definition
Pros: inexpensive, data already available, can ID potential risk factors / generate hypothesis
Cons: ecological fallacy, can't test hypotheses
Term
X-sectional
Pros & Cons
Definition
Pros: just at one time point so relatively cheap & quick
Cons: prevalence bias, selection bias, hard to study if there are rare diseases/exposures
Term
Cohort
Pros & Cons
Definition
Pros: rare exposures can be followed, can look at multiple outcomes, less selection bias, can find incidence rates, can look at temporality
Cons: expensive, long f/u, hard to study rare outcomes, loss to f/u
Term
Case-Control
Pros & Cons
Definition
Pros: cheapest, can study rare dxs, OR estimates RR
Cons: can't get relative risk, prevalence bias,
Term
Intervention
Pros vs Cons
Definition
Pros - can determine causality, reduces bias, multiple outcomes, measure incidence rates
Cons - most expensive, placebo effect, loss to f/u, non-compliance
Term
Sensitivity
Definition
true+/all+ diagnoses
a/a+c
test's ability to correctly ID individuals who have the disease
Term
Specificity
Definition
true-/all- diagnoses
D/B+D
tells you test's ability to correctly ID individuals who truly don't have dx
Term
Predictive Value Positive
Definition
A/A+B
true+ / all+ tests
If test positive, what is chance that have disease
Term
Predictive Value Negative
Definition
true-/all- tests
D/C+D
If I test negative, how sure are you I don't have disease
Term
Pretest probability
Definition
prevalence of untreated dx in population
Term
Posttest probability after positive test
Definition
A/A+B (same as predicted value positive)
Term
Posttest probability negative
Definition
C/C+D or 1-PVN
What is the chance that I have the disease after a negative test
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