Suppose a screening test for nicotine, the salivary cotinine test, is researched
ID: 3063119 • Letter: S
Question
Suppose a screening test for nicotine, the salivary cotinine test, is researched in 500 randomly selected persons. The results are given in the table below. The status of the smokers is known through interviewing and is not the test. The test in question is the Salivary Cotinine Test.
Smoking Status
+ Salivary Cotinine
- Salivary Cotinine
Totals
Smoker
95
5
100
Non-Smoker
20
380
400
Totals
115
385
500
What is the false positve rate of this test in percentage form rounded to the nearest tenth of a percent?
Smoking Status
+ Salivary Cotinine
- Salivary Cotinine
Totals
Smoker
95
5
100
Non-Smoker
20
380
400
Totals
115
385
500
Explanation / Answer
False positive as the name suggests is False "Positive"
ie the test calls the person as a smoker but in reality the person is not a smoker
In the above table
Non smoker who is called positive is 20
Hence false positive is 20
The false positive rate is given by
False positive/(False positive+ True negative)
=20/(20+380)=20/400=0.05 = 5 percent
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