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Table 2 IRT parameter estimates (in logistic metric) of GHQ-12 and Affectometer-2 items

From: An evaluation of computerized adaptive testing for general psychological distress: combining GHQ-12 and Affectometer-2 in an item bank for public mental health research

Item Abbreviated item wording Nr. of times Administereda α t1 t2 t3 t4
θ true  ~ N(0,1) θ true  ~ U(-3,3)
GHQ 1 Able to concentrate 140 1105 1.75 −3.95 3.08 5.75 -
GHQ 2 Lost sleep 2295 2010 1.53 −0.32 1.99 3.63 -
GHQ 3 Play useful part 865 2627 1.27 −2.50 3.12 4.81 -
GHQ 4 Making decisions 560 2286 1.46 −3.07 3.97 6.08 -
GHQ 5 Under strain 4071 4265 1.87 −1.13 1.93 4.11 -
GHQ 6 Overcome difficulties 4618 2279 2.07 0.04 3.08 4.69 -
GHQ 7 Enjoy day-to-day activities 475 2152 1.42 −3.15 2.47 4.46 -
GHQ 8 Able to face problems 374 1947 1.59 −3.36 4.11 6.46 -
GHQ 9 Unhappy 7578 6138 2.94 0.01 3.17 5.48 -
GHQ 10 Lose confidence 4922 3077 2.31 0.39 2.93 5.07 -
GHQ 11 Worthless person 1055 2449 3.07 2.03 4.84 6.97 -
GHQ 12 Reasonably happy 1007 2757 1.39 −2.60 2.84 4.87 -
Aff 1 Life on the right track 8420 6903 2.01 −3.19 −0.01 1.58 3.80
Aff 2 Change life 3686 4405 1.58 −1.94 0.32 1.71 3.81
Aff 3 Future looks good 3168 4175 1.57 −3.35 −0.29 1.27 3.48
Aff 4 Best years are over 0 19 1.41 −0.02 1.47 2.56 3.70
Aff 5 Like yourself 1287 3031 1.08 −2.35 −0.14 1.33 3.16
Aff 6 Something wrong 3257 3066 2.15 0.74 2.49 3.86 5.77
Aff 7 Handle problems 751 2340 0.96 −1.81 0.38 1.60 3.25
Aff 8 Failure 4134 4193 3.35 1.48 4.03 5.48 8.33
Aff 9 Loved and trusted 1934 2901 1.29 −1.14 1.37 2.57 4.14
Aff 10 Left alone 0 9 1.34 0.60 2.06 3.19 4.81
Aff 11 Close to people 1893 3101 1.29 −1.25 1.47 2.58 4.70
Aff 12 Lost interest 0 8 1.82 1.40 2.79 4.41 6.52
Aff 13 Do whatever want 1016 2794 0.98 −2.65 −0.83 0.59 2.04
Aff 14 Life stuck 7780 8080 2.46 −0.80 1.69 3.12 5.01
Aff 15 Energy to spare 195 952 0.77 −3.84 −1.78 −0.16 1.61
Aff 16 Can’t be bothered 2493 3771 1.54 −1.56 1.04 2.48 4.91
Aff 17 Smiling a lot 1130 2881 1.28 −3.02 0.08 1.47 3.67
Aff 18 Nothing fun 3141 2230 1.67 −0.26 1.90 3.18 4.80
Aff 19 Thinking creatively 1299 3032 1.23 −2.88 0.04 1.60 3.81
Aff 20 Thoughts useless 6031 4153 2.06 −0.09 1.75 3.39 5.62
Aff 21 Satisfied 4655 4218 1.85 −3.98 −0.06 1.73 4.74
Aff 22 Optimistic 587 2307 0.92 −3.08 −0.34 0.93 2.91
Aff 23 Useful 954 2727 1.11 −2.58 0.41 1.86 3.87
Aff 24 Confident 1579 3226 1.61 −3.10 0.13 1.88 4.21
Aff 25 Understood 303 1370 0.83 −2.65 0.03 1.63 3.27
Aff 26 Interested in others 24 132 0.80 −1.66 0.86 1.99 3.75
Aff 27 Relaxed 4299 4703 1.66 −3.42 −0.26 1.41 3.70
Aff 28 Enthusiastic 1719 3348 1.31 −3.76 −0.44 1.24 3.73
Aff 29 Good natured 670 2379 0.97 −1.91 1.06 2.46 4.90
Aff 30 Clear headed 1568 3238 1.24 −2.08 0.70 1.98 4.04
Aff 31 Discontented 4462 3809 1.87 −0.74 1.69 3.22 5.16
Aff 32 Hopeless 2079 3000 3.02 1.63 3.67 5.55 7.84
Aff 33 Insignificant 2923 2417 2.32 0.93 3.02 4.58 6.39
Aff 34 Helpless 2409 2541 2.22 1.23 2.98 4.33 6.08
Aff 35 Lonely 0 9 1.64 0.31 2.04 2.98 4.89
Aff 36 Withdrawn 5565 5027 2.59 0.71 2.82 4.62 7.02
Aff 37 Tense 2763 3937 1.58 −1.67 0.75 2.19 4.24
Aff 38 Depressed 7865 6862 3.00 0.36 2.72 4.30 6.30
Aff 39 Impatient 40 231 0.77 −2.03 0.29 1.62 4.07
Aff 40 Confused 0 10 1.49 0.32 2.27 3.56 5.23
  1. aNumber of times the items was administered out of 10,000 simulated CAT administration for SEM = 0.32, MLE and UW-FI item selection algorithm