Answer: Individual interviews
Explanation: An individual interview can be seen as an experimental method of acquiring information from an original source to gather non-numerical information with a small number of respondents to discuss in detail their viewpoints on a specific idea, program or circumstance.
Here, the Marine Midland Bank sent out their researchers to discuss with the head of each household in the community the reason for not checking accounts and credit cards with the bank. It can be carried out in 15-60 minutes.