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36 Cards in this Set
- Front
- Back
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What is a case-control study?
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Compares a group of people with disease to a group without; observational and retrospective
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What is a cohort study?
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Compares a group with a given risk factor to a group without to assess whether the risk factor increases the likelihood of disease; observational and prospective
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What is a cross-sectional study?
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Collects data from a group of people to assess the frequency of disease (and related risk factors) at a particular point in time.
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What is a twin concordance study?
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Compares the frequency with which both monozygotic twins or both dizygotic twins develop a disease
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What is an adoption study?
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Compares siblings raised by biologic vs. adoptive parents
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What is a clinical trial?
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Experimental study involving humans - compares therapeutic benefits of 2 or more treatments, or of treatment and placebo
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What is the purpose of phase 1 clinical trials?
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Assess safety, toxicity, and pharmcokinetics
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What is the purpose of phase 2 clinical trials?
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Assess treatment efficacy, optimal dosing, and adverse effects
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What is the purpose of phase 3 clinical trials?
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Compares new treatment to the current standard of care
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What is a meta-analysis?
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Study that pools data from several studies to come to an overall conclusion
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What are some possible limits of meta-analysis?
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Quality of individual studies or bias in study selection
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What is sensitivity? What is it used for?
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Proportion of all people with disease who test positive; screens diseases with low prevalence; SNOUT = Sensitivity rules out
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What is specificity? What is it used for?
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Proportion of all people without disease who test negative; confirmatory test after a positive screening test; SPIN = specificity rules in
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What is positive predictive value?
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Proportion of positive test results that are true positive
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What is negative predictive value?
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Proportion of negative test results that are true negative
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What is odds ratio for case control studies?
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Odd of having disease in exposed group divided by odds of having disease in unexposed group
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What is relative risk for cohort studies?
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Relative probability of getting a disease in the exposed group compared to the unexposed group
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What is attributable risk?
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The difference in risk between exposed and unexposed groups, or the proportion of disease occurrences that are a result of the exposure
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What is precision?
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The consistency and reproducibility of a test; the absence of random variation in a test
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What is accuracy?
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The trueness of test measurements
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What is selection bias?
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Nonrandom assignment to study group
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What is recall bias?
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Knowledge of presence of disorder alters recall by subjects
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What is sampling bias?
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Subjects are not representative relative to general population
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What is late-look bias?
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Information gathered at an inappropriate time
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What is procedure bias?
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Subjects in different groups are not treated the same
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What are the ways of reducing bias?
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1. Blind studies (double blind is better); 2. Placebo responses; 3. Crossover studies (each subjects act as own control); 4. Randomization
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What is the null hypothesis?
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Hypothesis of no difference - no association between the disease and the risk factor in the population
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What is the alternative hypothesis?
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Hypothesis that there is some difference - some association between the disease and the risk factor in the population
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What is a Type I error (alpha)?
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Stating that there is an effect or difference when none exists
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What is p?
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Probability of making a type I error; typically judged against a preset level such as 0.05 which means that there is a less than 5% chance that the data will show something that is not really there
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What is a Type II error (beta)?
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Stating that there is not an effect or difference when one exist
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What is power?
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Probability of rejecting null hypothesis when it is in fact false, or the likelihood of finding a difference is one in fact exists
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What does power depend on?
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1. Total number of end points experienced by population; 2. Difference in compliance between treatment groups (differences in the mean values between groups); 3. Size of expected effect
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What is a t-test?
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Checks difference between the means of 2 groups
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What is an ANOVA?
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Checks difference between the means of 3 or more groups
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What is x^2?
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Checks difference between 2 or more percentages or proportions of categorical outcomes (not means values)
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