Top: probability that a source with a given T_bol> 70 K will have T_bol,ext< 70 K, marginalizing over a uniform foreground A_V extinction distribution up to the listed value (shown in color). There is no Class 0 contamination from Class I models with T_bol> 400 K for the A_V values we consider here. Bottom: probability that a source is correctly classified as a Class 0 source (has T_bol< 70 K).