BEHAV SCIENCE Flashcards
Equations for sensitivity
TP / TP + FN
1 - false negative rate
Equations for specificity
TN / TN + FP
1-false positie rate
Equation for PPV
TP/TP + FP
Remember that if there is a high prevalence – > high PPV
Equation for NPV
TN/TN + FN
Remember that if there is a high prevalence – > low NPV
Equation for odds ratio
(a/c) / (b/d) or ad/bc
Used in case-control studies
Odds that the group with the disease was exposed to a risk factor (a/c) divided by the odds that the group without the disease (controls) was exposed
Equation for relative risk
a/(a+b) / c/(c+d)
Used in cohort studies
Risk of developing disease in exposed group divided by risk in unexposed group
Equation for attributable risk
a/(a+b) - c/(c+d)
Equation for # needed to treat
1/ARR
Absolute risk reduction equation
Absolute reduction in risk associated with tx as compared to a control (e.g. 8% of people who receive a placebo vaccine develop flu vs. 2% who receive a flu vaccine, then ARR = 8-2=6%
Equation for # needed to harm
1/attributable risk
Equation for incidence
of new cases in specified time period/population at risk during same time period
Equation for prevalence
# of existing cases/population at risk prevalence = incidence rate x average disease duration
Define Berkson’s bias
Studies performed on patients that have been hospitalized – type of selection bias.
This would make the patients more likely to have comorbidities.
Define procedural bias
Subjects in different groups are not treated the same -e.g., more attention is paid to treatment group, stimulating greater adherence.
Rank the values of mean, median, and mode in a positively skewed distribution.
Mean > median > mode
Longer tail on right
Rank the values of mean, median, and mode in a negatively skewed distribution.
Mean < median < mode
Define type I error
There is an effect or difference when none exists –also known as a false +
Define type II error
There is not an effect or difference when one exists –false negative error
3 ways to increase power (1-B)
Increase sample size
Increase expected effect size
Increase precision of measurement
Equation for confidence interval
mean +/- Z (SEM)
Z values for 90%, 95,%, and 99% CI
90: 1.65
95: 1.96
99: 2.57
Equation for SEM
SEM = SD / sq root of sample size
When is it important for a patient with a tetanus prone wound to receive a tetanus vaccine?
If the pt had or =3 doses, should receive vaccine if:
its been >10 years since and the wound is minor
its been >5 years since and the wound is high risk (if it has dirt or poop in it)
Which adult populations should receive a pneumonia vaccine? There’s 11.
> or = 65 y.o COPD, asthma Long-term care facilities Smokers Residents CVD HIV DM Liver disease Asplenia CSF leaks
