Who is most likely to join an interest group? *

Those with more education and also have higher income.

Explanation:

An interest group is referred to as an organization that tries to influence a particular decision by the government in order to achieve a certain goal.

They perform electoral functions, and also educate the public. It should be noted that the people that are more educated and have a high income are likely to join interest group because they are willing to invest their energy and time and also want to be invoiced with regards to happenings around them and have a say.