1. An apparatus comprising: at least one processor; a memory coupled to the at least one processor; a cohort analysis mechanism residing in the memory and executed by the at least one processor that analyzes an input case representing a question and finds cohorts with similar attributes to the input case to infer an attribute for the input case, provides a refined input case that includes the inferred attribute, and answers the question using the refined input case; and wherein the cohorts are entities with similar characteristics to an entity of the input case and available in a corpus of data.