Synesthesia is a phenomenon that has been estimated to occur in only a few people in a million. because of its rarity, researchers are likely to choose which research method to study it?

The most appropriate method for finding a conclusion would be the Case Study. This method constitutes of a way to investigate qualitatively and without strict rules. It's recommended for researchers looking for in depth information about a specific individual, person, group, institution and so forth.

i'll just take the points xd

its d i know cause i've been googling it