The level of lead in the blood was determined for a sample of 152 male hazardous-waste workers ages 20-30 and also for a sample of 86 female workers, resulting in a mean 6 standard error of 5.5 ± 0.3 for the men and 3.8 ± 0.2 for the women ("Temporal Changes in Blood Lead Levels of Hazardous Waste Workers in New Jersey, 1984-1987," Environ. Monitoring and Assessment, 1993: 99-107). Calculate an estimate of the difference between true average blood lead levels for male and female workers in a way that provides information about reliability and precision.