What constitutes a valid basis for an expert's opinion, and give an example.

• A. The foundation includes data, methods, and reasoning used; example: relying on test results and established literature.
• B. The expert's personal belief
• C. Hearsay statements only
• D. The opinion without explanation

Answer: (A)

A valid expert opinion must be grounded in data, methods, and reasoning. The expert should base conclusions on relevant information or data (such as measurements, test results, observations, or established literature), apply recognized methods or techniques to analyze that data, and clearly show how the data lead to the conclusion through logical reasoning. For example, an expert in materials science might analyze fatigue test results and cite published standards to explain how the observed crack patterns indicate material fatigue under specific loading, then walk through how the data and methods support the final conclusion. This shows why the opinion is reliable and persuasive, rather than simply reflecting personal belief or unsubstantiated statements. Personal belief by itself isn’t a sufficient basis; hearsay statements alone aren’t adequate either; and an opinion that presents no explanation or data cannot demonstrate how the conclusion was reached.