Final answer:
The bias described is the False consensus effect where an individual assumes that their opinions are held by the majority of people.
Step-by-step explanation:
The bias described in the question is known as the False consensus effect. This bias occurs when an individual assumes that their opinions or beliefs are shared by the majority of people. The individual may think that their own views are representative of a larger group, even when there is no evidence to support this assumption.
For example, if someone believes that most people agree with their political views simply because their immediate social circle holds similar beliefs, it would be an example of the false consensus effect. This bias can lead to an overestimate of the prevalence of one's own opinions or beliefs among the general population.