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Table 2 Performance of Greedy and Optimal Algorithm at Different Levels of Caliper

From: Methodologic considerations in the design and analysis of nested case-control studies: association between cytokines and postoperative delirium

Match Algorithm

Age Caliper

GCP Caliper

Number of Pairs

Mean Distance

Sum of Distance

Greedy

1

1

7

0.99

6.90

Optimal

1

1

7

0.99

6.90

Greedy

2

2

21

1.79

37.51

Optimal

2

2

21

1.76

36.89

Greedy

3

3

26

2.06

53.63

Optimal

3

3

26

2.05

53.48

Greedy

4

4

32

2.68

85.81

Optimal

4

4

34

2.99

101.7

Greedy

5*

5

34

3.01

102.45

Optimal

5*

5

39

3.79

147.79

  1. *Caliper is defined to be the minimum allowable difference between the case and the control. In our study, we used a caliper of five for age and GCP, and zero for the other four categorical variables
  2. GCP general cognitive performance
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BMC Medical Research Methodology

ISSN: 1471-2288

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