How is a hypothesis best defined?

A hypothesis is best defined as a theory supported by empirical data because it represents a testable prediction or explanation based on prior knowledge and observations. In scientific inquiry, a hypothesis is often formulated to guide the research process, enabling investigators to make predictions about the outcomes of experiments or observations. It is not merely speculation; rather, it is grounded in existing knowledge and sets the stage for further testing and validation.

In contrast, the other options describe concepts that do not fully capture the essence of a hypothesis. A proposed solution without evidence indicates a lack of foundational support, failing to align with the systematic approach of hypothesis formulation. A speculative assumption suggests a lack of empirical basis, which is contrary to the purpose of a hypothesis in research. An untested theory, while potentially close in nature to a hypothesis, lacks the critical component of empirical data that supports it. Therefore, the definition emphasizing a hypothesis as a theory that is backed by empirical data is the most accurate and relevant for scientific practices, especially in fire investigation where evidence is crucial for establishing facts.