Periods | N | Mean | Std. Deviation | Std. Error Mean | ||
1961-1976 | 16 | 12.0267 | 0.92421 | 0.23105 | ||
1977-1993 | 16 | 12.4541 | 0.70933 | 0.17733 | ||
1994-2009 | 16 | 13.3933 | 0.69768 | 0.17442 | ||
Periods | t | df | Sig. (2-tailed) | Mean Difference | 95% Confidence Interval of the Difference | |
Lower | Upper | |||||
1961-1976 | 52.052 | 15 | 0 | 12.02669 | 11.5342 | 12.5192 |
1977-1993 | 70.23 | 15 | 0 | 12.45407 | 12.0761 | 12.832 |
1994-2009 | 76.788 | 15 | 0 | 13.39329 | 13.0215 | 13.7651 |