Behavioral Science Flashcards
study population in cohort study
Compares a group with a given exposure or risk factor to a group without such exposure.
Ruling in vs. out
Negative test in a highly sensitive test rules out disease. Highly specific test rules in disease. (SNOUT/SPINN)
Other expression for sensitivity
1- false-negative rate
Effect of lowering test cutoff
Increased sensitivity, decreased specificity, increased NPV, decreased PPV (just think about it as increasing the # of FP and decreasing the nuber of FNs)
Effect of raising test cutoff
Increased specificity, decreased sensitivity, increased PPV, decreased NPV (similarly just think of it as increasing the # of FNs and decreasing the # of FPs).
Attributable risk
Difference in risk between exposed and unexposed groups, or the proportion of disease occurrences that are attributable to the exposure (eg, if risk of lung cancer in smokers is 21% and risk in nonsmokers is 1%, then 20% of lung cancer risk in smokers is attributable to smoking).
If 21% of smokers develop lung cancer vs. 1% of nonsmokers, what is the relative risk?
21
absolute risk reduction
Difference in risk (NOT proportion) attributable to interention as compared to a control (eg, if 8% of people who receive a placebo vaccine develop the flu vs. 2% of people who receive a flu vaccine, then ARR = 8% - 2% = 6% = .06
Number needed to harm
Number of patients who need to be exposed to a risk factor for 1 patient to be harmed.
Relation between precision and statistical power
Increased precision, increased statistical power
Statistical power definition
1-beta
random error vs. systematic error
random error decreases precision in a test, systematic error decreases accuracy in a test.
Berkson bias
Study population selected from hospital is less healthy than general population.
Healthy worker effect
Study population is healthier than the general population
Non-response bias
Participating subjects differ from nonrespondents in meaningful ways.
Procedure bias
Subjects in different groups are not treated the same.
Observer-expectancy bias
Researcher’s belief in the efficacy of a treatment changes the outcome of that treatment.
pygmalion effect
observer-expectany bias. AKA self-fulfilling prophecy
Crossover study
Subjects act as their own controls.
Lead-time bias
early detection confused with increased survival
How do you mitigate lead-time bias?
Measure “back-end” survival (adjust survival according to the severity of disease at the time of diagnosis).
normal distribution
mean = median = mode
Variance definition
(SD)^2
Standard error of the mean (SEM)
Estimate of how much variability exists between the sample mean and the true population mean.