Respuesta :
Answer:
predictive value of a positive test = 18.18%
predictive value of a negative test = 94.03%
Step-by-step explanation:
Sensitivity = 60% = 0.6
Specificity = 70% = 0.7
Let True Positive = TP
True Negative = TN
False Negative = FN
[tex]Sensitivity = \frac{TP}{TP + FN} \\0.6 = \frac{TP}{TP + FN} \\0.6TP + 0.6FN = TP\\0.4TP = 0.6FN\\TP = 1.5 FN[/tex]
[tex]Specificity = \frac{TN}{TN + FP} \\0.7 = \frac{TN}{TN + FP} \\0.7TN + 0.7FP = TN\\0.7FP = 0.3 TN\\TN = 7/3 FP[/tex]
Prevalence = 10% = 0.1
Three hundred people are screened, [tex]T_{total} = 300[/tex]
Total number of people having the disease, [tex]T_{disease} = ?[/tex]
[tex]Prevalence = \frac{T_{disease} }{T_{total} } \\0.1 = \frac{T_{disease} }{300 }\\T_{disease} = 30[/tex]
[tex]T_{disease} = TP + FN\\30 = TP + FN[/tex]
But TP = 1.5 FN
30 = 1.5 FN + FN
30 = 2.5 FN
FN = 30/2.5
FN = 12
TP = 1.5 FN = 1.5 * 12
TP = 18
[tex]FP + TN = T_{total} - T_{disease} \\FP + TN = 300 - 30\\FP + TN = 270\\FP + \frac{7}{3} FP = 270\\\frac{10}{3} FP = 270\\FP = 27 * 3\\FP = 81[/tex]
81 + TN = 270
TN = 189
To calculate the Predictive value of positive test (PPT)
[tex]PPT = \frac{TP}{TP + FP} * 100\\PPT = \frac{18}{18+81} * 100\\PPT = \frac{18}{99} * 100\\PPT = 18.18 \%[/tex]
To calculate the Predictive value of negative test (PNT)
[tex]PPT = \frac{TN}{FN + TN} * 100\\PPT = \frac{189}{189+12} * 100\\PPT = \frac{189}{201} * 100\\PPT = 94.03 \%[/tex]
