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Ely, Berbaum, Bergus et al. (1996) 1st Analysis

Reader and case sample combinations needed for 0.80 power based on the data of:

Ely JW, Berbaum KS, Bergus GR, Thompson BH, Levy BT, Graber MA, Evans ER, Bedell DA, Fick DS. Diagnosing left lower lobe pneumonia: usefulness of the 'spine sign' on lateral chest radiographs. Journal of Family Practice 1996;43:242-8.

Readers: 6 board certified family physicians

Analysis 1 Cases: 65 patients with pneumonia, 83 patients without pneumonia

Rating: probability of pneumonia on a 5-point scale (5=definite pneumonia)

Conditions: (1) only the PA view, (2) PA and Lateral views.

 

ROC Model = PropROC, Parameter = AUC,

AUCs = 0.853, 0.855, respectively.

Readers = 6, Cases = 148,

MS( Treatment*Reader )= 0.06586383,

MS( Treatment*Case ) = 0.13339134,

MS( Treatment*Reader *Case ) = 0.08949374.

 

Given a number of readers are available, we compute the number of cases needed when treating readers and cases as random factors, when treating cases as a random factor and readers as a fixed factor, and treating readers as a random factor and cases as a fixed fracture.

 

AUC Difference = 0.03

Readers

Readers

and Cases

Random

Cases

Random

Readers

Random

3

394

650

444

4

343

520

346

5

309

442

281

6

284

390

237

7

265

353

205

8

251

325

181

9

239

303

162

10

229

286

146

11

221

272

134

12

214

260

123

13

208

250

114

14

203

242

106

15

199

234

100

 

AUC Difference = 0.05

Readers

Readers

and Cases

Random

Cases

Random

Readers

Random

3

257

236

324

4

192

189

206

5

157

161

149

6

136

142

117

7

122

129

97

8

112

119

82

9

104

111

72

10

98

105

64

11

93

99

57

12

89

95

52

13

86

92

48

14

83

89

44

15

80

86

41

 

AUC Difference = 0.10

Readers

Readers

and Cases

Random

Cases

Random

Readers

Random

3

103

61

143

4

64

49

71

5

48

42

47

6

40

37

35

7

35

34

28

8

32

32

23

9

29

30

20

10

27

28

20

11

25

27

20

12

24

26

20

13

23

25

20

14

22

24

20

15

22

23

20

 


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