A fixed and categorized impression of a group of people based on a predetermined set of qualities is

A fixed, categorized impression of a whole group based on a preset set of qualities is stereotyping.

It assigns the same rigid traits to every member regardless of individual difference.

Generalizing draws a broad conclusion but is not necessarily the fixed group image applied to persons.

Consistency is steadiness of behaviour or judgement, unrelated to group labelling.

Oversimplification reduces complexity but does not specifically fix categorized traits onto a group.

Stereotyping is a common perceptual barrier in intercultural communication.