Skip to main content

Table 3 Power (%)* of selected clinical record review (CRR) scenarios to detect a reduction (R) in the real harm rate (rHR) over a twelve month period

From: Can we quantify harm in general practice records? An assessment of precision and power using computer simulation

Practices (n)

Records reviewed (n)**

Power (%)

rHR = 2

rHR = 5

rHR = 10

rHR = 20

  

R = 50%

R = 20%

R = 50%

R = 20%

R = 50%

R = 20%

R = 50%

R = 20%

1

40

0

0

0

0

0

0

0

0

50

0

0

0

0

0

0

0

0

100

0

0

0

0

0

0

1

1

200

0

0

0

0

2

1

9

5

300

0

0

0

0

3

2

19

7

400

0

0

1

1

11

4

27

7

10

40

0

0

1

0

8

4

30

8

50

0

0

2

1

16

5

37

8

100

1

0

14

5

38

7

64

14

200

9

4

36

8

66

13

93

22

300

21

5

57

10

84

16

98

32

400

28

8

65

12

91

22

100

41

20

40

0

0

10

4

28

7

53

11

50

0

0

17

6

37

8

66

15

100

10

4

37

10

63

13

93

24

200

28

7

67

13

91

22

100

38

300

43

9

81

19

98

31

100

54

400

56

11

92

20

100

40

100

69

50

40

9

3

34

8

65

13

93

24

50

14

5

45

10

75

16

96

28

100

36

10

74

16

96

25

100

48

200

64

12

97

27

100

48

100

79

300

84 $

18 $

100

41

100

64

100

92

400

94

21

100

48

100

79

100

97

100

40

31

6

64

11

92

20

100

40

50

35

10

76

14

96

29

100

53

100

66

12

97

26

100

47

100

77

200

90

22

100

48

100

76

100

96

300

98

34

100

64

100

92

100

100

400

100

38

100

78

100

97

100

100

150

40

45

10

84

16

99

33

100

56

50

51

11

89

21

100

38

100

64

100

82

15

100

39

100

64

100

91

200

99

32

100

64

100

91

100

100

300

100

46

100

81

100

99

100

100

400

100

57

100

92

100

100

100

100

200

40

53

12

91

23

100

38

100

68

50

64

12

96

28

100

47

100

77

100

92

22

100

49

100

78

100

97

200

100

36

100

79

100

96

100

100

300

100

56

100

92

100

100

100

100

400

100

67

100

96

100

100

100

100

250

40

64

14

98

25

100

49

100

77

50

76

13

99

36

100

58

100

85

100

97

30

100

55

100

86

100

99

200

100

50

100

87

100

99

100

100

300

100

67

100

95

100

100

100

100

400

100

79

100

99

100

100

100

100

300

40

74

15

99

31

100

55

100

84

50

82

18

99

37

100

64

100

90

100

98

29

100

65

100

91

100

100

200

100

54

100

91

100

100

100

100

300

100

73

100

99

100

100

100

100

 

400

100

85

100

100

100

100

100

100

  1. *Power below the type I error rate of 5% is possible because analyses where the estimates failed to converge are counted as failure to detect change in the harm rate.
  2. **The total number of records reviewed during the twelve month period is shown. Each patient record was reviewed twice during this time.
  3. $Example: In this CRR scenario, 50 practices each reviewed 300 records (150 at the beginning and 150 at the end of twelve months) and had a baseline rHR of 2 incidents/100patients/year. Reductions of 50% and 20% over a twelve month period were detected with 84% (adequate) and 18% (inadequate) power respectively.
  4. Scenarios vary by numbers of practices reviewing records, number of records reviewed in each practice and rHR. Median rate ratios (MRR) between patients and practices are 2 and 1.2 respectively.