Periodical Group | Average AC | SD | Significance Level (p) |
A = 1959-1969 | 177 | 28 | A < C (0.0021); C < D (0.0066) |
B = 1970-1979 | 168 | 25 | A < D (<0.0001); C > E (<0.0001) |
C = 1980-1989 | 285 | 76 | B < C (0.0014) |
D = 1990-1999 | 383 | 112 | B < D (<0.0001) |
E = 2000-2010 | 126 | 104 | D > E (<0.0001) |