Table 2.

One-sample t-test analyses of the difference between Utøya students’ academic performance and national grade point average

	M	SD	n	95% CI for mean difference	p
Before the event: first year of HS	0.13	10.71	64	−2.54, 2.81	0.920
After the event: second year of HS	−4.26	12.22	58	−7.47, −1.05	0.010
After the event: third year of HS	−0.04	11.10	47	−3.30, 3.22	0.980

HS, high school.