The personality assessment which requires individuals to describe how two people in his/her life differ from a third, thus identifying an important personality construct is the:

Role construct repertory test

Explanation:

A role construct repertory test was proposed by Kelly. This test is about an individual to understand his/her world around him and to know the people who are around him.

This test allows a person to describe himself in his way. In this test, the person has to tell the name of the person whom he knows. After that, the person has to compare himself from the listed three people whom he knows. For instance, a person can compare with father, mother, and self and tell about the similarities and dissimilarities among three people.