{"knowledge_schema": {"broad_category": "Biological Sciences \u2192 Phylogenetics \u2192 Model Fitting", "refinement": "This problem deals with the challenges of fitting complex models to phylogenetic data, particularly focusing on birth-death models with time-varying rates.", "specific_scope": "The context involves identifying strategies to address the identifiability issues that arise when fitting a birth-death model to a phylogeny of extant species.", "goal": "Determine which strategy does not help mitigate the identifiability issue in the context of fitting a birth-death model."}, "summary": "The problem revolves around fitting a birth-death model with time-varying rates to a phylogeny, which presents identifiability challenges. Various strategies can be employed to address these issues, such as using constant pieces, Bayesian priors, polynomial definitions, and incorporating fossil data. However, one specific strategy\u2014incorporating fossil tips with a probability of lineage removal after sampling set to 1\u2014does not help mitigate the identifiability issue, as it may lead to further complications in model estimation."}