Your question is Explain Your PhD Research Topic. Take a moment with it on the right.
Talk me through your thinking if you like. When you're confident, submit your answer and I'll grade it like a real screen (7/10 or better passes).
Explain your PhD research topic and the mathematical models you utilized.
Summarize the scientific problem, identify the model classes you used, and explain the assumptions, parameters, estimation methods, and validation approach. Be prepared to connect the mathematics to the conclusions your research supported and to discuss limitations.
The interviewer is assessing whether you can communicate technical research clearly and distinguish a model's structure from the data-fitting procedure. Keep the discussion focused on your own research and use equations or a concrete example where helpful.