Investigators want to assess the accuracy of self-reported smoking status. Parti

Question

Investigators want 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 the presence or absence of nicotine. The laboratory assessment is considered the truth about nicotine. Use the data in the following table to answer the questions. Hint: Be careful of how the cells are arranged.

Nicotine Absent

Nicotine Present

Self-Reported Non-Smoker

82

32

Self-Reported Smoker

3

97

a. What is the sensitivity of self-reported smoking status?

b. What is the specificity of self-reported smoking status?

c. What is the positive predictive value of the laboratory assessment?

d. What is the negative predictive value of the laboratory assessment?

Nicotine Absent

Nicotine Present

Self-Reported Non-Smoker

82

32

Self-Reported Smoker

3

97

Explanation / Answer

First rearrange table as

Smoker Non smoker

POsitive 97 3

Negative 32 82

Sensitivity = 97/(97+32) = 97/109

Specificity = 82/(82+32) = 41/57

Positive predictive value = 97/100 = 0.97

Negative pred value = 82/119

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