Depicting older workers as less involved in their work, less motivated, and haveing higher absenteeism than their younger counterparts int he workplace is a stereotype based on

This is a stereotype based on age. Stereotypes are assumptions about the characteristics, behaviors or thoughts of groups of people who share similar characteristics, although there is no evidence to corroborate that the assumptions are true. Stereotypes can be cultural, social or ethnic. Stereotypes based on age are those in which characteristics are attributed to people according to their age.

I hope my answer can help you.