Answer: DESCRIPTIVE RESEARCH.
Explanation: Descriptive research is a type of research that is designed to depict in an accurate way the participants and reaserch tools used in a research work.
Descriptive research is all about describing people who take part in the research work and the research tools used.
It can be done by viewing or recording the research tools and draws conclusion from it.
Descriptive design can be in the form of Case study,Field Observation and Survey.
So Jiwon can use any of the above methods to find out if there is a relationship between caffeine and candy sales for college students.
She can produce a small amount of candy,and watch the outcome on the part of the students before venturing on producing larger amounts.