Table 3. Summative testing results.

	Original design (7 participants, 28 scenarios)	UCD (8 participants, 32 scenarios)	Difference (95% CI, p -value)
Task completion with no errors	35.7%	65.6%	29.9% (3.9–56.5%, p  = 0.03)
Severe errors (per scenario)	0.5	0.125	−0.375 (−0.58 to −0.17, p  = 0.002)
Moderate errors	0.29	0.28	−0.005 (−0.29 to 0.29, p  = 0.97)
Mean time per scenario (sec)	87.4	95.4	8.0 (−37.3 to 21.4, p  = 0.57)
Mean change in quiz grade	−2.9%	10%	12.9% (−5.4 to 31%, p  = 0.15)

Abbreviations: CI, confidence interval; UCD, user-centered design.