Table 5. Correlation coefficients among sleep duration, social jetlag and daytime sleepiness (N=133)
| Variables | r (p) |
| 1. SDWD | 2. SDFD | 3. SDWN | 4. SDFN | 5. SJLD | 6. SJLN | 7. DS |
| 2 | .077 (.376) | 1 | | | | | |
| 3 | .135 (.122) | -.039 (.654) | 1 | | | | |
| 4 | .204* (.018) | .189* (.029) | .250** (.004) | 1 | | | |
| 5 | .033 (.703) | -.516** (<.001) | -.009 (.919) | -.049 (.579) | 1 | | |
| 6 | -.010 (.908) | .013 (.886) | -.159 (.067) | .207* (.017) | -.015 (.865) | 1 | |
| 7 | -.007 (.937) | -.117 (.181) | -.028 (.748) | -.060 (.493) | .168 (.054) | -.034 (.698) | 1 |
SDW=sleep duration on workdays; SDF=sleep duration on free days; D=day-shift; N=night-shift; SJL=social jetlag; DS=daytime sleepiness.