Statistical Evaluation of Diagnostic Tests: Sensitivity, Specificity, and Predictive Values
Analyzes diagnostic test accuracy using statistical methods such as sensitivity and specificity.
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Statistical Evaluation of Diagnostic Tests: Sensitivity, Specificity, and Predictive
Values
Screening
Exercise 1
A screening test for a newly discovered disease is being evaluated for its effectiveness and sensitivity as
a screening test in industry. In order to determine the effectiveness of the new test, it was administered
to 880 workers. Of those, 120 of the individuals diagnosed with the disease tested positive for it. Results
from the test showed a negative test finding for 50 people with the disease. A total of 40 people without
the disease tested positive for it.
Create a 2x2 table for this data:
Test findings/ Disease status Disease No disease Total
Positive test 120 (A) 40 (B) 160
Negative test 50 (C) 670 (D) 720
Total 170 710 880
1. What is the prevalence rate of the disease?
Prevalence rate of disease = ே ௪௧ ௗ௦௦
ே ௦௨ௗ = (170/880)*100 = 19.3
2. What is the sensitivity of the test?
Sensitivity of the test = (A / A+C)*100 = (120/170) * 100 = 70.58
3. What is the specificity of the test?
Specificity: D/(D+B) × 100 = (670/710) * 100 = 94.36
4. What is the percentage of false negatives?
FalseNeg = (1 - Sensitivity) * Prevalence
=(c/a+c)*prevelance
= 5.673
5. What is the percentage of false positives?
FalsePos = (1 - Specificity) * (1 - Prevalence)
=(b/b+d)*(no of people with no disease/N)*100
=4.551
6. What is the accuracy of the test?
Accuracy = no of correct assessment/total no of assessments= (A+D/N)*100= 89.72 %
Exercise 2
Two different tests previously developed to measure stress in individuals are selected: Stress Test Alpha
Battery (STAB) and Stress Test Uniform Battery (STUB). The sensitivity and specificity of these two tests
are:
Values
Screening
Exercise 1
A screening test for a newly discovered disease is being evaluated for its effectiveness and sensitivity as
a screening test in industry. In order to determine the effectiveness of the new test, it was administered
to 880 workers. Of those, 120 of the individuals diagnosed with the disease tested positive for it. Results
from the test showed a negative test finding for 50 people with the disease. A total of 40 people without
the disease tested positive for it.
Create a 2x2 table for this data:
Test findings/ Disease status Disease No disease Total
Positive test 120 (A) 40 (B) 160
Negative test 50 (C) 670 (D) 720
Total 170 710 880
1. What is the prevalence rate of the disease?
Prevalence rate of disease = ே ௪௧ ௗ௦௦
ே ௦௨ௗ = (170/880)*100 = 19.3
2. What is the sensitivity of the test?
Sensitivity of the test = (A / A+C)*100 = (120/170) * 100 = 70.58
3. What is the specificity of the test?
Specificity: D/(D+B) × 100 = (670/710) * 100 = 94.36
4. What is the percentage of false negatives?
FalseNeg = (1 - Sensitivity) * Prevalence
=(c/a+c)*prevelance
= 5.673
5. What is the percentage of false positives?
FalsePos = (1 - Specificity) * (1 - Prevalence)
=(b/b+d)*(no of people with no disease/N)*100
=4.551
6. What is the accuracy of the test?
Accuracy = no of correct assessment/total no of assessments= (A+D/N)*100= 89.72 %
Exercise 2
Two different tests previously developed to measure stress in individuals are selected: Stress Test Alpha
Battery (STAB) and Stress Test Uniform Battery (STUB). The sensitivity and specificity of these two tests
are:
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Subject
Statistics