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Table 2 Description of SCQ scores, reliability, item convergent and discriminant validity, and meaningfulness

From: Assessing the impact on caregivers of patients with schizophrenia: psychometric validation of the Schizophrenia Caregiver Questionnaire (SCQ)

    Reliability Confirmation of the structure Meaningfulness
         Distribution-based methods Anchor-based methods
          Patient minimally improved Patient minimally worsened
SCQ domains # of item Mean Score (SD) Cronbach’s alfa* ICC* Item-domain correlationsa # items meeting convergent validityb # items meeting discriminant validityc SD \( \times \sqrt{\left(1-\alpha \right)} \) Mean change Mean change
HI-TS 17 27.8 (23.4) 0.96 0.87 - - - 5.13 -3.96 7.67
HI-P 3 27.0 (27.3) 0.85 0.82 0.62-0.75 100 % 33 % 11.09 -6.75 10.42
HI-E 6 30.0 (24.8) 0.89 0.81 0.63-0.75 100 % 83 % 8.59 -2.23 8.78
HI-S 3 26.4 (26.1) 0.80 0.75 0.60-0.66 100 % 0 % 12.21 -3.16 1.49
HI-DL 5 26.5 (24.3) 0.87 0.81 0.59-0.76 100 % 40 % 9.26 -4.83 8.39
EC 2 19.9 (24.7) 0.69 0.76 0.49 100 % 100 % 14.37 -0.86 3.13
FA 1 32.0 (36.0) NA 0.63 NA NA NA NA -6.90 8.04
PD 2 36.7 (27.5) 0.57 0.75 0.37 0 % 0 % 18.64 -8.62 6.25
WP 2 42.0 (28.7) 0.70 0.75 0.54-0.71 100 % 100 % 12.93 -7.04 6.55
PC 3 34.0 (29.9) 0.79 0.71 0.71 100 % 100 % 12.45 -1.29 4.02
FDP 1 37.9 (39.6) NA 0.70 NA NA NA NA -8.62 -2.68
FIC 1 26.0 (32.1) NA 0.75 NA NA NA NA 0.86 1.79
ODC 1 28.6 (31.6) NA 0.75 NA NA NA NA -6.90 16.96
  1. SD Standard deviation; α = reliability coefficient (Cronbach’s α); ICC Intraclass correlation coefficient, NA not applicable as single-item dimension, HI-TS Humanistic impact – total score, HI-P Humanistic impact - Physical, HI-E Humanistic impact - Emotional, HI-S Humanistic impact - Social, HI-DL Humanistic impact - Daily life, EC Exhaustion with caregiving, FA Feeling alone, PD Patient Dependence, WP Worries for the patient, PC Perception of caregiving, FDP Financial dependence of the patient, FIC Financial impact of caregiving, ODC Overall difficulty of caregiving
  2. Description of SCQ scores, internal consistency reliability and item convergent and discriminant validity data were obtained at baseline in the caregiver analysis set (N = 358). Test-retest reliability data were obtained between baseline and month 3 in caregivers whose patient’s severity was stable between the two assessments (N = 147). Analyses supporting meaningful change in SCQ domain scores were calculated using distribution-based methods at baseline in the caregiver analysis set (N = 358) and anchor-based methods in patients minimally improved at Month 6 (N = 58) and patients minimally worsened (N = 28)
  3. *Reliability coefficient is considered acceptable if > 0.70
  4. aRange of correlations between each item and its domain score
  5. bItem convergent validity criterion: correlation between an item and its domain score should be ≥0.40
  6. cItem discriminant validity criterion: each item should correlate higher with its domain score than with the other domain scores