11.Given a test in which there is overlap of the test results for diseased and n
ID: 174411 • Letter: 1
Question
11.Given a test in which there is overlap of the test results for diseased and non-diseased individuals (e.g., normal individuals are found who have test results ranging in value from 8 to 15, and diseased individuals are found who have test results ranging in value from 12 to 25, so that in the range of values 12 to 15 there are both normal and diseased individuals), if you move the cutoff value toward the normal population (lower numbers in this example), the specificity will _____________________ .
A. Increase
B. Decrease
13.A single search (search ‘A’) of a database retrieved a total of 8,734 documents, of which 429 pertain to the topic being studied. Several additional searches on the topic of interest were also conducted and these additional searches plus search ‘A’ retrieved a total of 12,832 distinct documents, of which 1,987 pertained to the topic of interest. Given all of the above information, with respect to search ‘A’, what quantities can be calculated?
A. Precision, recall, and relative recall
B. Precision and recall
C. Recall and relative recall
D. Precision and relative recall
14. A new retrieval algorithm is being evaluated using a test database, constructed for that purpose. A single search (search ‘A’) of the database retrieved a total of 6,400 documents, of which 1,129 pertain to the topic being studied. Several additional searches on the topic of interest were also conducted and these additional searches plus search ‘A’ retrieved a total of 7,395 distinct documents, of which 1,488 pertained to the topic of interest. The person who constructed the database tells you that there are a total of 10,500 documents in the database, of which 1,750 are pertinent to the topic of your search. Given all of the above information, with respect to search ‘A’ what quantity (quantities) (recall, precision, or relative recall) can be calculated?
A. Precision, recall, and relative recall
B. Precision and recall
C. Recall and relative recall
D. Precision and relative recall
Explanation / Answer
11 B. The specificity will decrease because when you lower cutoff two things happen
- first the true positives increase TP
- secondly the False Positives increase too FP but more than increase in TP
i.e both TP and FP increases but FP increase>>> TP increase
- so looking at a equation and applying the above change we see that
the Specificity = TN / ( TN + FP ) decreases (by virtue of FP increase ..a denominator)
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