Final answer:
An individual given official permission to carry out certain job-related activities is known as an authorized person. A researcher pondering the attributes that make an employee suitable for a job would likely be a personality psychologist, delving into how personality traits impact work performance.
Step-by-step explanation:
A person that is approved or assigned by the employer to perform a specific type of duty or duties, or to be at a specific location or locations on the jobsite, is an authorized person. The term authorized implies that the person has been given official permission to perform certain actions or tasks within an organization. For example, an authorized employee may have the approval to operate certain machinery, access specific areas, or handle certain materials that others may not be permitted to engage with without similar authorization.
Answering your related question, a researcher interested in what factors make an employee best suited for a given job would most likely identify as a personality psychologist. This field of psychology focuses on individual differences, including personality traits, that affect how people perform in work settings. Such a psychologist would be interested in how various personality attributes contribute to an employee's success or fit for a specific role within a company.