A study to determine the sensitivity and specificity of a new test for celiac di
ID: 3199769 • Letter: A
Question
A study to determine the sensitivity and specificity of a new test for celiac disease is conducted on 7642 people. Studies have shown that celiac disease occurs at a rate of 1.32%. Your sample has the same prevalence of celiac disease. You find that 99 people with celiac disease tested positive with the new test. You also have a total of 7495 negative test results in your study. CALCULATE THE SENSITIVITY of this test.
Question 1 options:
A) 68.71%
B) 99.97%
C) 98.02%
D) 99.36%
E) 67.35%
A study to determine the sensitivity and specificity of a new test for macular degeneration is conducted on 2430 people. Macular degeneration occurs at a rate of 16.72%. Your sample has the same prevalence of macular degeneration. You find that 377 people with macular degeneration tested positive with the new test. You also have a total of 561 positive test results in your study. CALCULATE THE SPECIFICITY of this test.
Question 2 options:
A)
83.29%
B)
98.45%
C)
92.86%
D)
67.20%
E)
90.91%
A)
83.29%
B)
98.45%
C)
92.86%
D)
67.20%
E)
90.91%
Explanation / Answer
Q1)
Given:
new test for celiac disease is conducted on population = P = 7642
the people with celiac disease tested positive with the new test.= TP = 99
the people with negative test results = FN+TN = 7495
People who doesn't have celiac disease but had a positive result = FP = P-(FN+TN)-TP = 48
Rate of celiac disease = 0.0132
The total number of people with celiac disease = TP+FN = 0.0132*7642 = 100.87 = 101
=> FN =101-99 = 2 => TN=7495-2 = 7493
Therefore sensitivity = TP/(TP+FN) = 99/(99+2) = 0.9802 = 98.02%
Therefore the answer is (C).
Q2)
Given:
new test for macular degeneration is conducted on population = P = 2430
the people with macular degeneration tested positive with the new test.= TP = 377
the people with positive test results = FP+TP = 561
People who doesn't have celiac disease but had a positive result = FP = 561-377=184
People who had a negative result = TN+FN = P-(FP+TP) = 2430-561 = 1869
Rate of celiac disease = 0.1672
The total number of people with celiac disease = TP+FN = 0.1672*2430 = 406.3 = 406
=> FN =406-377=29 => TN=1869-29 = 1840
Therefore specificity = TN/TN+FP = 1840/1840+184 = 0.90909 = 90.91%
Therefore answer is (E).
Therefore the answer is (C).
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