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Table 3 Summary of Rasch analyses assessing the overall model fit performed in three stages along with the iterative revisions

From: Development and evaluation of the measurement properties of a generic questionnaire measuring patient perceptions of person-centred care

Analysis

Item residual

Person residual

Chi-square interaction

Psi

T test n (%, CI)

Mean

SD

Mean

SD

Value

DF

P

Original version

0.355

2.413

−0.296

1.464

371.1

160

< 0.001

0.84

15 (3.35%, 1.8–4.8%)

Thresholds ordered

−0.052

1.880

−0.347

1.416

330.5

160

< 0.001

0.85

16 (3.57%, 2–5.1%)

Items 13, 18 deleted

0.322

1.561

−0.383

1.521

180.3

144

0.022

0.85

16 (3.80%, 2.2–5.4%)

  1. Values highlighted in bold in the probability column indicate statistical significance at the 0.05 level after Bonferroni adjustment for the original version, with thresholds ordered set at 0.0025 for 20 items and with two items deleted set at 0.0027 for 18 items
  2. Independent t tests were performed with eight items divided into two subsets representing most diversity along a continuum. Each subset included > 15 thresholds for the original version and > 12 thresholds for the version with thresholds ordered and with two items deleted
  3. DF degrees of freedom
  4. P probability value
  5. Psi Person separation index reported with extrapolated person values included
  6. CI confidence interval reported as lowest to highest