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Table 3 Planned participants and clusters recruitment to targets in cluster trials

From: Statistical analysis of publicly funded cluster randomised controlled trials: a review of the National Institute for Health Research Journals Library

Characteristics

n

%

Mean (SD)

Median

Range

IQR

Original individual participant target sample size (N = 84b)

≤ 300

11

13

10,035 (31357)

1250

136–250,000

550–4466

301–600

11

13

    

601–900

13

15

    

901–1200

3

4

    

1201–1500

11

13

    

1501–1800

3

4

    

> 1800

29

35

    

Not reported

3

3

    

Final individual participant target sample size (N = 84b)

≤ 300

11

13

9372 (30173)

1212

136–250,000

534–4258

301–600

11

13

    

601–900

14

17

    

901–1200

5

6

    

1201–1500

11

13

    

1501–1800

3

4

    

> 1800

27

32

    

Not reported

2

2

    

Original individual participant target sample size met (N = 86)

Yes

57

66

    

No, but >= 80% met

14

16

    

No and < 80% met

9

11

    

Final individual participant recruitment target met (N = 86)

Yes

58

67

    

No, but 80% >= of target met

17

20

    

No and < 80% of target met

6

7

    

Not reported

5

6

    

Revised original individual participant target sample size (N = 86)

Yes, upward

13

15

    

Yes, downward

9

10

    

Yes, direction not reported

4

4

    

No

61

71

    

Original cluster recruitment target met (N = 86)

Yes

68

79

    

No, but >= 80% met

9

11

    

No, and < 80% met

1

1

    

Not reported

8

9

    
  1. bTwo studies were excluded because the original and final targets were expressed in person-years of observation and not specific number of participants [41, 54]. N = total number of trials; n = counts observed in each level of a variable; SD = standard deviation; IQR = interquartile range. Not reported means that the information of interest was not considered and/or provided in the trial