For the calculation of sample size,we used the SPSS
Sample Power3.0 software,through the model of difference
between means of two groups.The primary variable,the
Pittsburgh Sleep QualityIndex(PSQI)score,was utilized as a
reference for the calculation and the data were determined
from the results of Selvietal.(2012),who also studied the
quality of sleep in relationship to chronotype in a sample of
university students