Final answer:
Psychologist Raymond B. Cattell significantly advanced psychometric testing by pioneering the use of factor analysis in personality research, which led to the creation of the 16 Personality Factor Questionnaire.
Step-by-step explanation:
Raymond B. Cattell's significant contribution to psychometric testing is that he pioneered factor analysis in personality research. Cattell's work notably led to the development of a personality assessment called the 16 Personality Factor Questionnaire (16PF), which is based on 16 factors he identified as dimensions of personality. These dimensions include traits such as warmth, reasoning, and emotional stability, and are used to construct a multifaceted view of an individual's personality. His methodology allows personality traits to be scored over a continuum rather than just present or absent, providing a more nuanced understanding of personality. Cattell's application of factor analysis to personality traits was instrumental in advancing the field of personality psychology and continues to influence psychometric testing today.