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Table 4 GAFS-8 graded response model parameters and equivalent factor loadings for full sample

From: Improving the measurement of alexithymia in autistic adults: a psychometric investigation of the 20-item Toronto Alexithymia Scale and generation of a general alexithymia factor score using item response theory

TAS-20 Item # a1 d1 d2 d3 d4 λ h2
1 2.802 3.092 − 0.689 − 2.740 − 6.336 0.855 0.731
2 2.190 3.478 0.491 − 0.931 − 3.841 0.790 0.623
6 2.335 2.090 − 0.805 − 2.413 − 5.497 0.808 0.653
9 2.402 3.137 0.072 − 1.434 − 5.170 0.816 0.666
11 1.870 2.745 − 0.234 − 1.505 − 4.340 0.740 0.547
12 1.235 1.739 − 0.526 − 1.636 − 3.644 0.587 0.345
13 1.892 2.054 − 0.646 − 2.231 − 4.771 0.743 0.553
14 1.538 1.285 − 1.133 − 2.201 − 4.361 0.671 0.450
  1. Parameters estimated using maximum marginal likelihood based on Bock–Aitkin EM algorithm. This model contained two groups: general population (θ fixed to M = 0, SD = 1 in this group) and autistic group (mean and SD of θ free to vary), with all item parameters constrained to equality between groups. TAS-20 = 20-item Toronto Alexithymia Scale; a1 = slope parameter; d1–d4 = item intercept parameters (more positive values indicate “easier” items); λ = factor loading on single factor; h2 = communality (squared factor loading)