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Table 4 Average inter-item correlation and Cronbach’s Alpha scores for study outcome measures at baseline

From: An empirical evaluation of the SF-12, SF-6D, EQ-5D and Michigan Hand Outcome Questionnaire in patients with rheumatoid arthritis of the hand

  Average Inter- item correlation Cronbach’s Alphas Internal Consistency
MHQ 0.45 0.83 Good
EQ-5D (utility) 0.47 0.84 Good
EQ-5D (VAS) 0.48 0.84 Good
SF-12 (PCS) 0.46 0.84 Good
SF-12 (MCS) 0.52 0.87 Good
SF-6D 0.44 0.83 Good
  1. Internal consistency is considered unacceptable for α <0.5, poor for 0.6 > α ≥ 0.5, questionable for 0.7 > α ≥ 0.6, acceptable for 0.8 > α ≥ 0.7, good for 0.9 > α ≥ 0.8 and excellent for α ≥ 0.9 [32, 34]