4. Model Selection and Evaluation# 4.1. Protocols for Quantification 4.1.1. Artificial-Prevalence Protocol (APP) 4.1.2. Natural-Prevalence Protocol (NPP) 4.1.3. Uniform Prevalence Protocol (UPP) 4.1.4. Personalized Prevalence Protocol (PPP) 4.1.5. References 4.2. Tuning Hyperparameters 4.2.1. References 4.3. Evaluation Metrics 4.3.1. Single Label Quantification (SLQ) Metrics 4.3.2. Regression-Based Quantification (RQ) Metrics 4.3.3. Ordinal Quantification (OQ) Metrics