Cohort | Mean | Std. Deviation | Std. Error Mean | 95% Confidence Interval of the Difference | t | df | Sig. (2-tailed) | |
Lower | Upper | |||||||
2017 | −14.212 | 13.668 | 1.474 | −17.143 | −11.282 | −9.643 | 85 | 0.0001 |
2018 | −11.337 | 14.264 | 2.103 | −15.573 | −7.101 | −5.391 | 45 | 0.0001 |
Total | −13.210 | 13.892 | 1.209 | −15.602 | −10.818 | −10.925 | 131 | 0.0001 |