
Total

Dead

CFR

CFR

X deaths

Y deaths


#

#

%

X/Y

%

%


Scenario A

X

500

0

0.0
   
Y

1500

30

2.0

0.0
  
Both X & Y

500

30

6.0
   
Total

2500

60

2.4
   
AllX

1000

30

3.0
 
50%
 
All Y

2000

60

3.0

1.0
 
100%

Scenario B

X

500

6

1.2
   
Y

1500

30

2.0

0.6
  
Both X & Y

500

30

6.0
   
Total

2500

66

2.6
   
All X

1000

36

3.6
 
55%
 
All Y

2000

60

3.0

1.2
 
91%

Scenario C

X

500

10

2.0
   
Y

1500

30

2.0

1.0
  
Both X & Y

500

30

6.0
   
Total

2500

70

2.8
   
All X

1000

40

4.0
 
57%
 
All Y

2000

60

3.0

1.3
 
86%

 In Scenario A, X does not have any mortality by itself, but when the subjects with both criteria are included X and Y appear to have the same mortality rate. Using only criterion X would select those children with zero mortality and those with both X and Y criteria and miss all the deaths related to criterion Y
 In Scenario B, there is a lower mortality with criterion X, however when the subjects fulfilling both criteria are included the relative case fatality rates are reversed so it appears now that X is a superior diagnostic parameter than Y. Yet its use only identifies 55% of the deaths
 In Scenario C, both X and Y have the same mortality rates but when the subjects with both criteria are included Y appears to be a superior diagnostic criterion. Yet this only leads to identification of 57% of deaths
 The columns % deaths shows the percentage of all deaths that would occur in children with criterion X or criterion Y as the single diagnostic tool. Criterion Y identifies more deaths than criterion X, but when the children with both criteria are included criterion X appears to have a higher case fatality rate