. Author manuscript; available in PMC: 2017 Jul 18.

Published in final edited form as: Psychol Assess. 2014 Feb 17;26(2):513–527. doi: 10.1037/a0035768

Table 2.

Classical Item Analysis

Test	No. of items	N	Cronbach’s α reliability	Average interitem correlation	Adjusted (corrected for overlap) item–total correlation
Test	No. of items	N	Cronbach’s α reliability	Average interitem correlation	Minimum	Mean	Maximum
PROMIS Depression	28	747	0.98	.64	.71	.79	.86
CES-D	20	747	0.93	.42	.44	.63	.82
PROMIS & CES-D	48	747	0.98	.53	.45	.72	.86
PROMIS Depression	20	748	0.98	.70	.74	.83	.88
PHQ-9	9	748	0.91	.55	.58	.70	.80
PROMIS & PHQ-9	29	748	0.98	.62	.60	.78	.88
PROMIS Depression	15	1,120	0.98	.76	.80	.86	.90
BDI-II	21	1,120	0.96	.57	.56	.74	.82
PROMIS & BDI-II	36	1,120	0.98	.62	.56	.78	.88

Note. PROMIS Depression = Depression subscale of the Patient-Reported Outcomes Measurement Information System; CES-D = Center for Epidemiologic Studies Depression Scale; PHQ-9 = 9-item Patient Health Questionnaire; BDI-II = Beck Depression Inventory–II.