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Table 5 Item response theory alpha and item-total correlations at PROMISE-2 baseline

From: Reliability and validity of the 6-item Headache Impact Test in chronic migraine from the PROMISE-2 study

Item Item content Pearson (α1) Polychoric (α2)
HIT-6 total score 0.82 0.85
   Alpha if item removed
1 Severe pain 0.82 0.87
2 Limits daily activities 0.78 0.81
3 Lie down 0.81 0.84
4 Too tired 0.76 0.81
5 Felt fed up or irritated 0.80 0.84
6 Limits concentration 0.76 0.80
   Item-total correlation
   Pearson Polychoric
1 Severe pain 0.42 0.58
2 Limits daily activities 0.64 0.84
3 Lie down 0.49 0.74
4 Too tired 0.71 0.83
5 Felt fed up or irritated 0.54 0.71
6 Limits concentration 0.72 0.87
  1. HIT-6 6-item Headache Impact Test