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Table 1 Two-by-two table for calculation of specificity and predictive values

From: Validity and reliability of data collected by community health workers in rural and peri-urban contexts in Kenya

 

Test results (CHW data)

 

Positive (+) (yes)

Negative (-) (no)

Research assistant data

Positive (+) (yes)

a

b

 

Negative (-) (no)

c

d

  1. Specificity = d / c+d
  2. Positive predictive value = a / a+c