FA - Behavioral Science Flashcards
Observational study: Case-control
Comparison? Variable? Time course? Reporting measure?
- ) Compares group of people with disease to group of people without disease
- ) Looks for prior exposure or risk factor
- ) Always retrospective
- ) Reported as ODDS RATIO (ad/bc)
Observational study: Cohort study
Comparison? Variable? Time course? Reporting measure?
- ) Compares group of people with exposure to group of people without exposure
- ) Looks for incidence of disease
- ) Can be prospective OR retrospective
- ) Reported as RELATIVE RISK ((a/a+b)/(c/c+d))
Observational study: Cross-sectional study
Method? Reporting measure?
- ) Collects data from a group of people to assess frequency of disease and related risk factors at a particular point in time
- ) Demonstrates disease prevalence and risk factor association
Quantifying risk: Odds ratio
Odds that the group with the disease (cases) was exposed to a risk factor (a/c) divided by the odds that the group without the disease (controls) was exposed (b/d) = ad/bc
Quantifying risk: Relative risk & attributable risk percent
1.) RR= Risk of developing disease in the exposed group divided by risk in the unexposed group = ((a/a+b)/(c/c+d))
If prevalence is low, RR~OR
2.) ARP= (Risk in exposed-risk in unexposed)/(risk in exposed)=(RR-1)/RR
Quantifying risk: Attributable risk & NNH
- ) The difference in risk between exposed and unexposed groups, or the proportion of disease occurrences that are attributable to the exposure =((a/a+b)-(c/c+d))
- ) NNH=1/AR
Quantifying risk: Absolute risk reduction & NNT
- ) Absolute reduction in risk associated with a treatment as compared to a control =(event rate in placebo group)-(event rate in treatment group)
- ) NNT=1/ARR
Precision
Reliability; affected by random error
Accuracy
Validity; affected by systematic error
Bias: Selection bias
Definition? Examples? Ways to avoid?
- ) Nonrandom assignment to participation in a study group
- ) Berkson’s bias, loss to follow up
- ) Randomization
Bias: Recall bias
Knowledge of presence of disorder alters recall by subjects
Bias: Sampling bias
Subjects are not representative of the general population so results are not generalizable
Bias: Late-look bias
Information gathered at an inappropriate time
Bias: Procedure bias
Subjects in different groups are not treated the same
Bias: Confounding bias
Definition? Ways to avoid?
- ) Occurs when factor is related to both exposure and outcome, but is not on the causal pathway; factor distorts or confuses effect of exposure on outcome
- ) Crossover studies, randomization, matching
Bias: Lead-time bias
Early detection confused with increased survival; seen with improved screening
Bias: Observer expectancy effect
Definition? Ways to avoid?
- ) When researcher’s belief in the efficacy of a treatment changes the outcome of that treatment
- ) Blinded studies
Bias: Hawthorne effect
When the group being studied changes its behavior owing to the knowledge of being studied
Statistical error type: Type 1 error (alpha)
Stating that there IS an effect or difference when none exists (mistakingly rejecting the null hypothesis/accepting the alternative)
Statistical error type: Type 2 error (beta)
Stating that there is NO effect or difference when one does exist (mistakingly accepting the null hypothesis/rejecting the alternative)
Power (1-beta)
Definition? Influenced by?
- ) Probability of rejecting the null hypothesis when it is actually false
- ) Increases with increased sample size, increased expected effect size, increased precision in measurement
95% and 99% Confidence intervals
- ) 95% CI: mean +/- 1.96*SEM
2. ) 99% CI: mean +/- 2.58*SEM