Table 3.

Standard error of measurement (SEM) for depression tests calibrated to the PROMIS metric

Test	Mean (SD)	Median	Interquartile range	Range
PHQ-9, PROMIS metric	4.9 (1.4)	4.6	3.5–6.6	2.8–8.3
PROMIS short form, PROMIS metric	3.5 (1.8)	2.6	1.8–5.5	1.5–7.5
PROMIS-simulated CAT, 9 items	2.7 (1.4)	2.0	1.7–3.4	1.4–5.2
PROMIS-simulated CAT, 8 items	2.8 (1.3)	2.2	1.8–3.4	1.5–5.2
PROMIS-simulated CAT, 3 items	3.7 (1.3)	3.2	2.7–5.6	2.3–5.6

Note that the data presented in the table refer to means and standard deviations of standard errors of measurement; smaller is better. The PROMIS metric uses a SD of 10; on the unadjusted IRT logit scale, then, a mean SEM of 4.9 corresponds to a mean SEM of 0.49 standard theta units