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Table 1 Contingency table for the observer agreement for cognitive impairment at cut-off −2 SD

From: Validation of a culturally modified short form of the McCarthy Scales of Children’s Abilities in 6 to 8 year old Zimbabwean school children: a cross section study

Assessment results cut-off −2 SD
Observer 1
Observer 2 Delayed Not Delayed Total
A B  
True positive False positive  
3 0 3
C D  
False negative True negative  
15 83 98
Total 18 83 101
  1. Sensitivity = A / A + C 3/18=17%.
  2. Specificity = D / B + D 83/83=100%.
  3. Total Agreement = A + D / A + B + C + D (3+83)/101=86%.
  4. Positive Predictive Value = A / A + B 3/3=100%.
  5. Negative Predictive Value = D / C + D 83/98=84%.
  6. Over-referral = B / A + B + C + D 0/101=0%.
  7. Under-referral = C / A + B + C + D 15/101=15%.
  8. Likelihood ratio—positive = Sensitivity / (1 – specificity) incalculable.
  9. Likelihood ratio—negative = (1 – sensitivity) / specificity .83.