Miss Jan DeJong is orderly, neat, fairly quiet, and shy. She enjoys reading in her spare time and belongs to a social club that includes three librarians, nine real estate agents, and eight social workers. A tendency to conclude that Jan must be one of the librarians would illustrate the powerful influence of:

Answer:The representativeness heuristic

Explanation:

When we want to make a decision about something but we don't have much information available we tend to rely on our pre-existing information to decide.

The representativeness heuristic is based on making a judgement by comparing what we see at that moment to what we already know then making a conclusion on that, so we think of what is more relevant to what we see based on what we know already.

Based on what we know about librarians we take that information and find it relevant to how Miss Jan Dejong is and conclude that she is librarian; this is known as representative heuristic.