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35 Cards in this Set
- Front
- Back
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Proportion of all people with disease who test positive
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Sensitivity
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Value approaching 1 desirable for ruling out disease
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Sensitivity (SNOUT) - SeNsitivity rules OUT
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Indicates low false negative rate
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Sensitivity
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Used for screening in disease with low prevalence
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Sensitivity
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TP/ (TP+FN) = 1-false negative rate
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Sensitivity
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Proportion of all people without the disease who test negative
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Specificity
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TN/ (TN+FP) = 1-false positive rate
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Specificity
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Value approaching 1 is desirable for ruling in
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Specificity
SPIN = SPecificity rules IN |
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Indicates low false positive rate
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Specificity
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Used as a confirmatory test after a positive test
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Specificity (E.g. HIV testing. Screen with ELISA. Confirm with Western Blot)
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Proportion of positive test result that are true positive
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Positive predictive value (PPV)
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Probability that person actually has the disease given a positive test result
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PPV
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TP/ (TP+FP)
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PPV
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Proportion of negative test results that are true negative
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Negative predictive value (NPV)
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Probability that person actually does not have the disease given a negative test result.
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NPV
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TN/ (FN+TN)
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NPV
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Type of error stating that there is an effect or difference when none exists (convicting an innocent man)
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Type I (alpha)
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False positive error
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Type I (alpha)
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Type of error stating that there is not an effect or difference when one exists (setting a guilty man free)
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Type II (beta)
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False negative error
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Type II (beta)
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Probability of rejecting null hypothesis when it is in fact false, or the likelihood of finding a difference if one in fact exists
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Power (1-beta)
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68% normal Gaussian distribution (NGD)
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1 standard deviation (SD)
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95% NGD
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2 SD
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99.7% NGD
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3 SD
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Incidence of disease in the exposed group - incidence of disease in the unexposed group
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Attributable risk
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1/absolute risk reduction (ARR)
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Number needed to treat (NNT)
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Compares a group of people with disease to a group without a disease
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Case-control study
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Example of case control study
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Odds ratio
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ad/bc = TP x TN/FP x FN
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Odds ratio
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Compares a group of people with a given risk factor to a group without a risk factor to assess whether the risk factor increases the likelihood of disease
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Cohort study
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Example of cohort
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Relative risk
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a(a+b)/c(c+d) = TP(TP+FP)/TN (TN+FN)
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Relative risk
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Incidence of disease in the exposed group - incidence of disease in the unexposed group
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Attributable Risk
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Control group's event rate - experimental group's event rate
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Absolute risk reduction (ARR)
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1/ARR
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Number needed to treat
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