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.
Calculate and interpret a 99% confidence interval for the difference between true means. Is uoride toothpaste beneficial?