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Table 2 Characteristics of Studies Reporting on Emergency Room Visits.*

From: Meta-analytic methods for pooling rates when follow-up duration varies: a case study

Study

Intervention Group

Control Group

Duration (Months)

Standardized Effect Size**

 

N

Mean ± SD

Rate

N

Mean ± SD

Rate

  

Alexander

11

0.60 ± 0.90

0.05

10

2.40 ± 2.10

0.20

12

-1.09

Christiansen

27

0.30 ± 1.20

0.03

15

0.20 ± 0.43

0.02

12

0.10

Clark

159

1.72 ± 4.20

0.14

73

2.49 ± 6.26

0.21

12

-0.16

Fireman

13

0.08 ± 1.14

0.01

13

1.00 ± 1.14

0.08

12

-0.78

Hughes

44

0.45 ± 1.05

0.04

45

0.60 ± 1.05

0.05

12

-0.14

Lewis

48

2.30 ± 2.98

0.19

28

3.71 ± 2.98

0.31

12

-0.47

McNabb

7

1.90 ± 4.72

0.16

7

7.40 ± 4.72

0.62

12

-1.09

Persaud

18

0.27 ± 0.57

0.05

18

1.00 ± 1.20

0.20

5

-0.76

Ronchetti

114

0.07 ± 0.32

0.01

95

0.23 ± 0.78

0.02

12

-0.28

Shields

101

0.54 ± 1.68

0.05

104

0.38 ± 1.68

0.03

12

0.09

Talabere

25

0.44 ± 0.77

0.15

25

1.08 ± 1.32

0.36

3

-0.58

Toelle

63

1.51 ± 2.31

0.25

51

1.67 ± 2.40

0.28

6

-0.07

  1. * N refers to the sample size, Mean ± SD refers to the mean number of events ± standard deviation, and rate refers to the total events per person-month. ** Standardized effect size was calculated for each study by subtracting control group mean from intervention group mean and dividing by the pooled SD.