Step 1: Understanding the Concept:
This question asks to identify a specific method of psychological assessment. Let's define the options:
Interview: A data collection method involving direct, spoken questions.
Self-report: A method where individuals provide information about themselves, typically through questionnaires or surveys.
Psychological test: A standardized instrument designed to measure psychological attributes.
Case-study: A comprehensive and in-depth investigation of a single person, group, or event. It often uses multiple methods (like interviews, tests, and observations) to gather rich, detailed information.
Step 2: Detailed Explanation:
The description in the question — "an in-depth study," "of the individual," considering "psychological attributes, psychological history," and "psycho-social and physical environment" — perfectly aligns with the definition of a case-study. A case-study is holistic, aiming to understand the person as a whole by examining various facets of their life. The other options (interview, self-report, psychological test) are tools that might be \textit{used within} a case-study, but they are not the comprehensive study itself.
Step 3: Final Answer:
The research method described is a Case-study.