# Table 2 The BIST item fit statistics and frequency distribution of responses categories ordered by Item Difficulty

Item Number Item description Item Difficultya
(Logits)
Item fit residual χ2 p Frequency distribution of response categories (0–3)
Cat-0 Cat-1 Cat-2 Cat-3
14 I feel tired during the day −0.86 − 0.94 2.21 0.33 18 34 34 18
1 Headache (my head hurts) −0.76 0.71 1.07 0.59 11 53 29 11
15 I sleep a lot more or can’t fall asleep − 0.54 1.51 0.99 0.61 27 27 34 16
11 I have trouble concentrating − 0.37 −0.44 1.83 0.40 24 39 3 11
8 It takes me longer to think −0.35 −1.31 1.39 0.50 25 40 27 12
9 I forget things −0.31 −0.10 0.20 0.90 24 37 33 10
4 I don’t like loud noises −0.34 0.70 0.25 0.88 25 36 30 11
12 I get easily annoyed −0.21 −0.01 0.26 0.88 26 38 31 9
2 My neck hurts −0.07 1.23 2.24 0.33 34 42 17 11
3 I don’t like bright lights 0.06 −0.52 0.42 0.81 33 36 27 8
13 I feel restless 0.53 0.39 0.41 0.81 46 38 14 6
10 I get confused easily 0.54 −0.76 1.46 0.48 48 30 20 6
7 I have trouble with my eyesight (vision) 0.68 1.57 3.63 0.16 47 35 18 4
5 If I close my eyes, I feel like I am at sea 0.98 −0.55 4.77 0.09 56 30 14 4
6 I feel like I will be sick 1.00 −0.04 0.54 0.77 61 30 9 4
1. χ2 Chi-square, p probability.
2. χ2 degree of freedom for items df = 2; Frequency distribution - extreme excluded; Response options in bold were endorsed by less than 10 people.
3. a = Item Difficulty (location) in logits ordered from easiest (Item 14, Tired) to most difficult (Item 6, Sick) items; negative logit values = easier items,
4. positive logit values = more difficult items.