Table 3.

Item response theory case classification difficulty index results.

Data set	CDIa range	Overall, mean (SD)	Point-biserial correlationsb		No death, mean (SD)	Death, mean (SD)	Two-tailed t valuec
			r value	P value			t test (df)	P value
MIMIC-IIId balanced	−1.81 to +2.16	0.00 (0.85)	0.37	<.001	−0.32 (0.79)	0.32 (0.80)	35.76 (8077)	<.001
MIMIC-III imbalanced	−1.70 to +2.27	0.00 (0.85)	0.35	<.001	−0.21 (0.80)	0.42 (0.80)	40.88 (12116)	<.001
eICUe balanced	−2.63 to +2.83	0.00 (0.80)	0.50	<.001	−0.40 (0.73)	0.40 (0.64)	86.18 (21939)	<.001
eICU imbalanced	−2.55 to +2.93	0.00 (0.81)	0.51	<.001	−0.29 (0.73)	0.59 (0.61)	109.09 (32909)	<.001

^aCDI: classification difficulty index.

^bBetween CDI and outcome (no death or death).

^cDifference between no death and death means.

^dMIMIC III: Medical Information Mart for Intensive Care.

^eeICU: electronic intensive care unit.