A lethality curve from Thrall et al. (26 ) illustrating the width of the 95% confidence interval with dose. LD = lethal dose. As described by Thrall et al., “PROBIT plot calculated 60-d lethality of total-body irradiated (TBI) rhesus macaques presented as percent mortality versus TBI dose (Gy). Dashed lines represent that 95% confidence interval and points reflect the actual experimental data. The cohorts were provided supportive medical care, as described by Farese et al. 2012. TBI was conducted using 6 MV LINAC-derived photons at a dose rate of approximately 0.8 Gy min^–1. The calculated LD50/60 [95% CI] was 7.43 Gy [6.92, 7.91.]” (Published and modified, with permission, from: Thrall KD, Love R, O'Donnell KC, Farese AM, Manning R, MacVittie TJ. An interlaboratory validation of the radiation dose response relationship (DRR) for H-ARS in the rhesus macaque. Health Phys 2015; 109:502–10.)