Many ancient Egyptian tombs were cut from limestone rock that contained uranium. Since most tombs are not well ventilated, guards, tour guides, and visitors may be exposed to deadly radon gas. In Radiation Protection Dosimetry (December 2010), a study of radon exposure in tombs in the Valley of Kings, Luxor, Egypt (recently opened for public tours) was conducted. The radon levels — measured in becquerels per cubic meter (Bq/m³) — in the inner chambers of a sample of 12 tombs were determined. Summary statistics follow: y̅ =  3,643 Bq/m³ and s = 4,487  Bq/m³ . Use this information to estimate, with 95% confidence, the true mean level of radon exposure in tombs in the Valley of Kings. Interpret the resulting interval.