Table 1.

Difficulty estimates for the JLO items (Form V).

Item Number	Difficulty
1	−1.023
2	−2.237
3	−2.988
4	−3.172
5	−2.770
6	−2.921
7	−1.668
8	−1.381
9	−2.318
10	−1.898
11	−3.132
12	−2.008
13	−1.751
14	−1.104
15	−1.043
16	−2.585
17	−1.913
18	−0.963
19	−1.278
20	−1.267
21	−1.023
22	−0.973
23	−0.913
24	0.235
25	−0.467
26	−0.750
27	0.028
28	−0.557
29	−0.350
30	−1.412

Difficulty is defined as the point at which the probability of successfully answering an item is 50%. Higher negative numbers indicate easier items.