Apsychologist studying cultural diversity who conducts a few lengthy interviews with members of various cultural communities is using

I believe the answer is: qualitative techniques.

qualitative techniques refers to the techniques that is used  in order to obtain the data that are not measurable by numbers (such as emotions, body language, principles, etc). Because of this lengthy interview or direct observations often became the most preferred methods to obtain such data.

the consumer demand because the members have to be aware if people are going to buy what they want to sell in this case either energy drinks or a car wash.

the works of justice saves things/people

the works of service things/people

explanation:

that's the best i can word it. hope it !