Table 1.

Summary of the properties of the ACE tool

Test property	Measure used	Acceptable results	Performance of the ACE tool
Content validity	Expert opinion	Test covers steps 1–4 of EBM	Acceptable
Item difficulty	Percentage of candidates who correctly answered the question	Wide range of results allows implementation across a wide range of participants including novice to expert	Ranged from 36% to 84%
Internal consistency	Cronbach’s alpha	Cronbach’s alpha 0.6-0.7 is considered acceptable, 0.70-0.90 good and >0.90 excellent	Cronbach’s α = 0.69
Internal reliability	Item-total correlation (ITC)	≥0.15 is considered acceptable	Ranged from 0.14 to 0.20 all items apart from three (0.03, 0.04 & 0.06)
Item discrimination index	Item discrimination index (ranges from −1.0 to 1.0)	All items should be positively indexed, ≥ 0.20 is considered acceptable	Ranged from 0.37 to 0.84
Construct validity	Mean scores three participant cohorts (EBM-novices, EBM-intermediate and EBM-advanced) compared by ANOVA	Significant differences in mean scores with EBM-advanced > EBM-intermediate > EBM-novice	On a 15-point test, mean scores were 8.6 EBM-novice; 9.5 EBM-intermediate; and 10.4 EBM-advanced (p < 0.0001)