A bifactor model supports unidimensionality of the International Knee Documentation Committee Subjective Knee Form in young active patients with anterior cruciate ligament tears: a retrospective analysis of a randomized controlled trial

Table 4 Reliability and unidimensionality of the International Knee Documentation Committee Subjective Knee Form (IKDC) bifactor model in young active patients with anterior cruciate ligament tears

Measure	Value	Description [13]
Omega (ω)
General	0.932	Estimate of internal reliability (analogous to Cronbach alpha for non-bifactor models)
Symptoms	0.716
Activity	0.845
ADLs	0.859
Sport	0.860
Omega Hierarchical (ω_H)
General	0.810	Proportion of systematic variance in total or subscale scores attributed to individual differences on the general factor or secondary factors, respectively
Symptoms	0.199
Activity	0.377
ADLs	0.124
Sport	0.528
Relative Omega (ω_R)
General	0.869	Proportion of reliable variance in the total scores due to the general factor, or reliable variance in subscale scores independent of the general factor
Symptoms	0.277
Activity	0.447
ADLs	0.144
Sport	0.614
Factor Determinacy (FD)
General	0.922	Correlation between factor scores and the factors
Symptoms	0.814
Activity	0.795
ADLs	0.817
Sport	0.898
Explained Common Variance (ECV)
General	0.584	Proportion of the common variance in total or secondary subscale scores explained by the general or secondary factors, respectively
Symptoms	0.062
Activity	0.090
ADLs	0.078
Sport	0.187
Percent Uncontaminated Correlations (PUC)	0.778	Proportion of covariance terms which only reflect variance from the general factor

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