To identify a relatively small number of the most basic personality traits, trait theorists have used

a. free associationb. factor analysisc. projective testsd. social cognitive theorye. the MMPI

Factor analysis have been used by trait theorists to identify a relatively small number of the most basic personality traits.

Factor analysis can be defined as a statistical method used to decrease a large numbers of variables to smaller numbers of factors. It is a widely used tools and is part of general linear model.