Fig 4. Top panel: Estimated σ and ρ as a function of ${\widehat{p}}_j$ for 20 areas in Greenland et. al [12], with loess smooth overlayed.

Bottom panel: Solid line represents OC curve for n = 60, d = 50 for p _l = .75, p _u = .9 design when σ and ρ are fixed at the mean value of $\widehat{\sigma }$ (left) and $\widehat{\rho }$ (right). Dashed line represents OC curve when σ and ρ vary over p according to the predicted loess smooth of $\widehat{\sigma }$ (left) and $\widehat{\rho }$ (right).