Please help me answer this following questions. As part of the study described i

Question

Please help me answer this following questions. As part of the study described in Problem 6, investigators wanted to assess the accuracy of self-reported smoking status. Participants are asked whether they currently smoke or not. In addition, laboratory tests are performed on hair samples to determine presence or absence of nicotine. The laboratory assessment is considered the gold standard, or truth about nicotine. The data are as follows: a. What is the prevalence of smoking? b. What is the sensitivity of self-reported smoking status? c. What is the specificity of self-reported smoking status? d. If someone tests positive for nicotine, what is the chance that they are a smoker? In other words, what is the PPV of Smoking?

Explanation / Answer

(A+C) Disease = 66

(a) Prevalence of smoking (= Totaldisease/ Total(Participants) × 100 = (66/160) x 100 = 41.25%

(b) Sensitivity of self reported smoking status(Sensitivity is the probability that a test will indicate 'disease' among those with the disease) = A/(A+C) × 100 = (54/66) x 100 = 81.82%

(c) Specificity of self reported smoking status(Specificity is the fraction of those without disease who will have a negative test result) = D/(D+B) × 100 = (80/94) x 100 = 85.11%

(d) PPV of smoking = A/(A+B) × 100 = (54/68) x 100 = 79.41%

Nicotine Present(Disease) Nicotine Absent(Non Disease) Total Self Reported Smoker(Positive) A = 54 B = 14 Positive= 68 Self Reported Non Smoker(Negative) C= 12 D = 80 Negative= 92 Total

(A+C) Disease = 66

(B+D) Non Disease= 94 160

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