Researchers collected the birth weights in kilograms of infants born on regular workdays, which are Monday through Friday, and on weekends, which are Saturday and Sunday, during one month. The weights for workdays are $3.6,3.4,3.5,3.7,3.3,3.5$. The weights for weekends are $3.2,3.4,3.3$. What is the difference in mean birth weight between workdays and weekends?