11. The level of lead in the blood was determined for a sample of 152 male hazardous-waste workers age 20—30 and also for a sample of 86 female workers, resulting in a mean 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, Envir.

y  59.8 x  65.6 Monitoring 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.