Table 2.

Results of unpaired t tests: Differences in practice exam scores graded by individual students versus a professional grader and student groups versus a professional grader

	Mean difference: individual students versus professional	Mean difference: student groups versus professional	n for individuals, groups	t statistic	p value (two-tailed)
Spring 2005: Week 5	0.89 ± 0.18	0.76 ± 0.23	96, 43	−0.47	0.64
Spring 2005: Week 10	1.81 ± 0.17	1.38 ± 0.24	94, 43	−1.43	0.15

Means are reported with SEs.