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Ely, Berbaum, Bergus et al. (1996) 2nd 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 2 Cases: 43 patients with pneumonia and 'spine sign', 83 patients without pneumonia   and spine sign.

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 = 0.891, 0.923, respectively.

Readers = 6, Cases = 126,

MS( Treatment*Reader ) = 0.11067224,

MS( Treatment*Case ) = 0.11576126,

MS( Treatment*Reader*Case ) = 0.07895497.

 

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

.

568

.

4

.

454

.

5

.

385

.

6

.

339

.

7

.

306

.

8

1154

282

929

9

743

262

550

10

568

247

392

11

469

235

304

12

406

224

249

13

362

215

210

14

330

208

182

15

305

201

161

Note: Cells containing a period indicate that more than 2000 cases would be required.

 

AUC Difference = 0.05

Readers

Readers

and Cases

Random

Cases

Random

Readers

Random

3

.

206

.

4

.

165

.

5

394

140

416

6

242

124

222

7

183

112

152

8

151

103

116

9

131

96

94

10

117

91

79

11

107

86

68

12

99

82

60

13

93

79

53

14

88

76

48

15

84

74

44

 

AUC Difference = 0.10

Readers

Readers

and Cases

Random

Cases

Random

Readers

Random

3

219

53

363

4

80

43

93

5

53

37

53

6

41

33

37

7

35

30

28

8

30

28

23

9

27

26

20

10

25

25

20

11

24

23

20

12

22

22

20

13

21

22

20

14

20

21

20

15

20

20

20

 


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