Which of the following is an example of an indirect reference group?

An indirect reference group is one that influences an individual's attitudes or behaviors without direct interaction or personal relationship. In the context of the given choices, a celebrity serves as an indirect reference group because individuals often admire and aspire to emulate public figures, even though they have no personal relationship with them. Celebrities can shape perceptions, trends, and consumer behavior through their public personas and marketing partnerships.

On the other hand, family members, close friends, and coworkers represent direct reference groups. These are people with whom an individual has personal relationships, and their opinions and behaviors profoundly affect the individual's choices and attitudes through personal interaction. Thus, celebrities, as part of popular culture, exemplify indirect influence, making them the correct choice in this scenario.