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