Table 3.

Description and Item Level Analysis of the Spanish NUMi Candidate Items

Item #	Item Description	CTT Difficulty	CTT Discrimination	IRT Difficulty	IRT Discrimination
1	Serum glucose goal for patient with diabetes	0.85	0.34	−1.28	1.37
2	Using a pain scale	0.86	0.50	−1.09	1.40
3	Interpreting percentage format for risk information	0.76	0.44	−0.71	1.32
4	Interpreting frequency format for risk information	0.76	0.50	−0.85	0.87
5	Interpreting small risk estimates with percent and frequency formats	0.49	0.56	0.20	0.62
6	Interpreting nutrition label	0.82	0.43	−1.31	0.73
7	Prostate screening test	0.46	0.48	0.002	0.81
8	Statistical significance	0.27	0.53	1.19	0.85

CTT Difficulty: Classical test theory difficulty calculated as % correct; CTT Discrimination calculated as item-total correlation. IRT Difficulty and Discrimination: Item response theory parameters determined by two-parameter model. Items included on each test. Items 7 and 8 were not included in the Spanish NUMi. The calibration of these items was done using the software BILOG.⁴⁶