TABLE 2.
PROMIS PPSM item statistics
| Item descriptive statistics | IRT parametersa | ||||||||
|---|---|---|---|---|---|---|---|---|---|
| Item | M | SD | % Floor (never) | % Ceiling (always) | a | b1 | b2 | b3 | b4 |
| I felt stressed. | 1.25 | 1.16 | 33.45 | 4.18 | 2.69/2.77 | −.48/−.48 | .32/.33 | 1.16/1.17 | 2.06/2.03 |
| I felt that my problems kept piling up. | 1.11 | 1.20 | 42.51 | 4.53 | 3.72/4.86 | −.18/−.17 | .50/.50 | 1.12/1.10 | 1.84/1.75 |
| I felt overwhelmed. | .94 | 1.09 | 48.08 | 2.44 | 3.81/3.80 | −.03/−.02 | .56/.58 | 1.39/1.42 | 2.10/2.08 |
| I felt unable to manage things in my life. | .97 | 1.11 | 46.69 | 2.79 | 3.77/3.12 | −.06/−.06 | .54/.57 | 1.31/1.39 | 2.10/2.18 |
| Everything bothered me (PPSM-8). | .88 | 1.08 | 48.78 | 3.14 | 2.67 | −.01 | .82 | 1.47 | 2.23 |
| I felt under pressure (PPSM-8). | .93 | 1.11 | 49.83 | 2.79 | 3.01 | .01 | .58 | 1.37 | 2.24 |
| I had trouble concentrating (PPSM-8). | 1.22 | 1.15 | 32.40 | 4.18 | 2.17 | −.57 | .49 | 1.21 | 2.24 |
| I felt I had too much going on (PPSM-8). | 1.16 | 1.19 | 40.07 | 4.53 | 2.97 | −.25 | .39 | 1.15 | 1.97 |
Note. a = IRT discrimination parameter; b1–4 = IRT difficulty parameters; IRT = item response theory; PPSM = Pediatric Psychological Stress Measure; PPSM-8 = eight-item PPSM, PPSM-4 = four-item PPSM; PROMIS = Patient-Reported Outcomes Measurement Information System.
a
In the IRT parameters section of the table, the discrimination and difficulty coefficients of the PPSM-8 are listed before the slash sign and the ones of the PPSM-4 are listed after the slash sign.