Epi 202 Lab 6.docx - Epi 202 Lab 6 1 In a study on 200 subjects radiographic detection of caries was compared to a gold standard based on a combination

# Epi 202 Lab 6.docx - Epi 202 Lab 6 1 In a study on 200...

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Epi 202 Lab 6 1.In a study on 200 subjects, radiographic detection of caries wascompared to a gold standard based on a combination of tests.Radiographs failed to detect 40% of the actual lesions anddetected caries at 5% of the sites where it was not detected by thegold standard. The results show that: a.Radiographs have a high sensitivity and low specificityb.Radiographs have a low sensitivity and high specificityc.Radiographs have a high sensitivity and high specificityd.Radiographs have a low sensitivity and low specificityAnswer: b 2. Consider the following table for self-reported hypertension versus true hypertension status obtained by blood pressure measurements. Calculate the sensitivity, specificity, false positive rate, predictive value positive and predictive value negative. Self vs. Measured HTN (E+) No HTN (E-) Total HTN (T+) 80 20 100 No HTN (T-) 3 47 50 Total 83 67 150 Sensitivity = P(E+|T+) = 80/83 = 0.96 Specificity = P(E-|T-) = 47/67 = 0.701 FPR = P(T+|E-) = 20/67 = 0.3 FNR = P(T-|E+) = 3/83 = 0.036 PPV = P(E+|T+) = 0.8 NPV = P(E-|T-) = 47/50 = 0.94 3. True or False If errors are made in the data collection phase of a cohort study such that a single binary exposure is mismeasured independently of the outcome of interest, then the relative risk estimated from this study may be biased either toward or away from the null. (Assume no other sources of the following: bias, confounding, effect modification or measurement error).

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• Summer '14
• FrancisCook