McNemar

set.seed(123)
tbl=rbind(c(30,20),
          c(25,125))
dimnames(tbl)=list(
  c('Si_C','No_C'),
  c('Si_C','No_C')
)
tbl

##      Si_C No_C
## Si_C   30   20
## No_C   25  125

mcnemar.test(tbl)

## 
##  McNemar's Chi-squared test with continuity correction
## 
## data:  tbl
## McNemar's chi-squared = 0.35556, df = 1, p-value = 0.551

(tbl[1,2]+tbl[2,1])/sum(tbl)

## [1] 0.225

#En cáncer un 22.5% e los diagnóstico son errados, esto es complejo