Table 4.

Posttest precision and sensitivity analyses (difficulty: P; discrimination: D) for the 14 BEDCI questions (all classes pooled, n = 580), split into the associated concepts they address

		Difficulty (P) (% expert-like)		Discrimination (D) (−1 to +1)
Core concept	BEDCI question number	Pre	Post	Pre	Post
Controls	1	80.0	85.0	0.21	0.24
	5	55.3	63.3	0.46	0.35
Hypotheses	2	40.2	38.6	0.34	0.25
	9	42.2	38.4	0.46	0.31
Biological variation	3	69.0	78.8	0.31	0.30
	10	37.4	43.6	0.15	0.35
Accuracy	4	58.6	58.5	0.50	0.35
Extraneous factors	6	49.7	69.0	0.49	0.51
	14	49.5	52.9	0.45	0.37
Independent sampling	7	50.3	52.6	0.52	0.52
	12	24.1	37.9	0.25	0.49
Random sampling	8	51.7	46.9	0.35	0.47
	13	63.6	70.5	0.31	0.32
Purpose of experiments	11	32.4	50.2	0.38	0.46