A screening test for bureaucratic pomposity disorder (BPD) has reasonably good s
ID: 3369289 • Letter: A
Question
A screening test for bureaucratic pomposity disorder (BPD) has reasonably good sensitivity and specificity, say 70% for both. (This means that, on average, seven out of every ten people who have BPD test positive and seven out of every ten who don't have BPD test negative.) Consider testing two different populations.
a. Officiousville has a population of 1000. Half the people in Officiousville have BPD. Suppose everyone in Officiousville gets tested. Fill out the table below. Then use it to compute the PPV and NPV for this test.
Test Result
Positive
Negative
Total
Disease
Present
500
Absent
500
Total
1000
Round the answers to two decimal places.
PPV =
NPV =
b. Mellowville also has a population of 1000, but only 10 people in the whole town have BPD. Fill out a table to show how the test would perform if you used it to screen Mellowville. Then compute the PPV and NPV for this test.
Test Result
Positive
Negative
Total
Disease
Present
10
Absent
990
Total
1000
Round the answers to three decimal places.
PPV =
NPV =
Test Result
Positive
Negative
Total
Disease
Present
500
Absent
500
Total
1000
Explanation / Answer
a)
for above:
PPV=true posiitve/total positive =350/500=0.7
NPV = true negative/ttoal negative =350/500=0.7
b)
PPV=7/304= 0.0230
NPV=693/696=0.9957
Test Result Positive Negative Total Disease Present 350 150 500 Absent 150 350 500 Total 500 500 1000Related Questions
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