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Table 3 Recruitment properties of the studies audited, stratified by presence of an internal pilot

From: Progression criteria in trials with an internal pilot: an audit of publicly funded randomised controlled trials

 

Internal pilot

(N = 97)

No internal pilot

(N = 37)

Total

(N = 134)

Total target sample size

n

97

36

133

Mean (SD)

945.1 (1400.0)

1171.8 (1460.3)

1006.5 (1414.6)

Median (IQR)

510.0 (350.0, 900.0)

625.0 (395.0, 1,349.2)

533.0 (360.0, 1,044.0)

Minimum, maximum

120, 9920

100, 8000

100, 9920

Recruitment target for internal pilot

n

69

–

69

Mean (SD)

135.2 (156.8)

–

135.2 (156.8)

Median (IQR)

100.0 (48.0, 162.0)

–

100.0 (48.0, 162.0)

Minimum, maximum

20, 1165

–

20, 1165

Proportion of sample size aimed to be recruited in internal pilot (%)

n

69

–

69

Mean (SD)

18.5 (10.4)

–

18.5 (10.4)

Median (IQR)

15.8 (10.2, 25.0)

–

15.8 (10.2, 25.0)

Minimum, maximum

2.3, 50

–

2.3, 50

Length of recruitment for full study (months)

n

96

35

131

Mean (SD)

28.6 (10.9)

22.3 (9.1)

26.9 (10.8)

Median (IQR)

24.0 (20.8, 36.0)

20.0 (16.5, 30.0)

24.0 (18.0, 36.0)

Minimum, maximum

11, 60

5, 45

5, 60

Length of recruitment for internal pilot (months)

n

96

–

96

Mean (SD)

9.4 (5.1)

–

9.4 (5.1)

Median (IQR)

8.5 (6.0, 12.0)

–

8.5 (6.0, 12.0)

Minimum, maximum

3, 30

–

3, 30

Proportion of recruitment length used in internal pilot (%)

n

95

–

95

Mean (SD)

33.5 (12.6)

–

33.5 (12.6)

Median (IQR)

33.3 (25.0, 40.8)

–

33.3 (25.0, 40.8)

Minimum, maximum

9.4, 68.8

–

9.4, 68.8

Number of centres involved in full study

n

91

30

121

Mean (SD)

20.9 (22.1)

19.9 (17.1)

20.6 (20.9)

Median (IQR)

14.0 (7.5, 25.0)

15.5 (6.0, 29.0)

14.0 (7.0, 26.0)

Minimum, maximum

1, 120

3, 70

1, 120

Number of centres involved in internal pilot

n

88

–

88

Mean (SD)

9.4 (11.6)

–

9.4 (11.6)

Median (IQR)

6.0 (4.0, 12.0)

–

6.0 (4.0, 12.0)

Minimum, maximum

1, 100

–

1, 100

Proportion of centres used in internal pilot (%)

n

86

–

86

Mean (SD)

56.8 (31.3)

–

56.8 (31.3)

Median (IQR)

49.0 (33.3, 100.0)

–

49.0 (33.3, 100.0)

Minimum, maximum

9.5, 100

–

9.5, 100

  1. IQR interquartile range, SD standard deviation