Answer:
Case study.
Step-by-step explanation:
The research of psychology are mostly based on the observation and experience of the individual. The psychologist must follows the proper rules and regulation of the research.
Dr, Smith research is based especially on the case study. These case study includes the collection of the data from the multiple source. The reaction of the individual is measured on the different visual sensation and different sounds. Quantitative data collection is mostly used in the case study of the Dr. Smith.
Thus, the answer is case study.