Public Health Sciences First Aid Flashcards
frequency of disease and frequency of risk-related factors are assessed in the present
what does this measure?
Cross-sectional study
disease prevalence
compares a group of people with a disease to a group without disease
what does this measure?
case control study
odds ratio (OR)
What are the four phases in clinical trials?
- small number of healthy volunteers - is the drug SAFE
- small number of pts with disease of interest - does it WORK
- large number of pts randomly assigned either to the treatment under investigation or to the best available treatment (or placebo) - any IMPROVEMENT
- postmarketing surveillance of pts after tx is approved - withdrawn from MARKET
Sensitivity equation
= TP/ (TP+FN)
Specificity equation
= TN/(TN+FP)
PPV equation
= TP/(TP+FP)
NPV equation
=TN/ (TN+FN)
Prevalence equation
= (TP+FN)/(TP+FN+FP+TN)
positive Likelihood ratio v negative Likelihood ratio
LR+ = sensitivity/ 1-specificity
LR- = 1-sensitivity/specificity
In regards to likelihood ratios, what are indicators of a very useful diagnostic test?
LR+ >10 and LR- <0.1
Odds ratio equation
= ad/cb
relative risk is generally used in what kind of studies?
what is the equation?
what are interpretations of RR scores?
cohort studies
= a/(a+b) // c/(c+d)
RR=1 then no association between exposure and disease
RR>1 then exposure associated with increased disease
RR<1 then exposure associated with decreased disease
difference in risk between the exposed and unexposed groups
attributable risks
the proportion of risk reduction attributable to the intervention as compared to a control
equation?
relative risk reduction
RRR = 1-RR
the difference in risk attributable to the intervention as compared to a control
equation?
Absolute risk reduction
ARR = (c/c+d) - (a/(a+b)
When talking about number needed to treat, a lower number indicates…
equation?
When talking about number needed to harm, a high number indicates…
equation?
better treatment => NNT = 1/ARR
safer exposure => NNH = 1/AR
study population selected from hospital is less healthy than general population
Berkson bias
The Hawthorne Effect is an example of what kind of bias?
measurement bias
What kind of bias is called Pygmalion effect?
observer-expectancy bias
when a factor is related to both the exposure and the outcome, but not on the causal pathway - factor distorts or confuses effect of exposure on outcome
confounding bias
early detection is confused with increased survival
lead-time bias
Stating that there is an effect or difference when none exists is called
Type I error (alpha)
false positive
Stating that there is not an effect or difference when one exists
Type II error (beta)
false negative
range of values within which the true mean of the population is expected to fall, with a specified probability
confidence interval
If the 95% CI for a mean difference between 2 variables includes 0, then
there is no significant difference and H0 is not rejected
If the 95% CI for odds ratio or relative risk includes 1, then
H0 is not rejected
If the CIs between 2 groups do not overlap, then
statistically significant difference exists
If the CIs between 2 groups overlap, then
usually no significant difference exists
prioritization of positive effects over negative effects (esp in hospice care) is known as
principle of double effect
