In psychology, factor analysis is a statistical method used to identify underlying relationships between variables by reducing a large set of variables to a smaller, more manageable set of factors. Essentially, factor analysis enables researchers to understand the data structure and identify variables that tend to cluster together, suggesting they are influenced by the same underlying factors (Gary R. VandenBos, 2015).

An example of an assessment instrument that has delineated factors is the MMPI-2 (Minnesota Multiphasic Personality Inventory-2). The MMPI-2 contains 567 true-false questions addressing mental health symptoms, beliefs, and attitudes that are grouped into scales (clusters of items) that address specific clinical problems such as depression or anxiety. An MMPI scale allows the clinician to compare the client's responses with those of thousands of others. To gain a perspective on the patient's test results, the MMPI-2 scores are compared to the normative sample, a large representative sample of people from across the United States. This comparison allows the interpreter to determine if the person's responses are different from those of people who do not have mental health problems. Suppose the patient obtains scores in the extreme ranges, for example, on the Depression scale (compared with the normative sample). In that case, they are likely to be experiencing problems comparable to the clinical samples of depressed clients that have been studied. The MMPI-2 results provide the practitioner with a clearer understanding of the patient's symptoms and personality features, helping to identify potential areas for exploration in therapy.

Factor analysis is a statistical technique used to identify underlying dimensions or factors that explain the relationships between variables in a dataset. The MMPI-2 (Minnesota Multiphasic Personality Inventory-2) comprises a range of scales and subscales designed to evaluate various aspects of personality and psychopathology. These scales can be broadly categorized into clinical, content, and validity scales. 

The original 10 clinical scales are designed to measure various psychological and psychiatric traits. They include Hypochondriasis (Hs), Depression (D), Hysteria (Hy), Psychopathic Deviate (Pd), Masculinity-Femininity (Mf), Paranoia (Pa), Psychasthenia (Pt), Schizophrenia (Sc), Hypomania (Ma), and Social Introversion (Si). The MMPI-2 content scales provide specific insights into various psychological issues by focusing on distinct themes and problems, offering a more detailed picture of an individual's personality and difficulties. Some examples include anxiety, depression, fears, obsession, bizarre mentation, anger, cynicism, low self-esteem, social discomfort, and antisocial practices. The MMPI-2 validity scales help determine the reliability of a test taker's responses and identify potential issues, such as faking good or bad, or random responding. These scales help ensure the accuracy of the personality profile by flagging potentially invalid profiles as Over-Reporting/Exaggerating Symptoms (Faking Bad) or  Under-Reporting/Minimizing Symptoms (Faking Good).

Both exploratory factor analysis (EFA) and confirmatory factor analysis (CFA) have been used in research with the MMPI-2 and MMPI-2-RF, each serving different purposes. The difference between them is that EFA is used to identify underlying factors within a dataset, while CFA tests a pre-existing theoretical model of those factors. Studies have used EFA to explore the structure of the MMPI-2-RF items about specific diagnoses like schizophrenia and ASD, and to compare the MMPI-2 and MMPI-2-RF in assessing personality characteristics. CFA has been used to examine how existing MMPI-2-RF scales map onto a latent structure and to test the psychometric properties of subscales within the MMPI-2 PSY-5 modes.

References

Butcher, J. N. (1999). A beginner's guide to the MMPI-2. American Psychological Association

Gary R VandenBos, E. (2015). APA concise dictionary of psychology.

Floyd AE, Gupta V. Minnesota Multiphasic Personality Inventory. [Updated 2023 Apr 24]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK557525/

Quilty LC, Bagby RM. Psychometric and structural analysis of the MMPI-2 Personality Psychopathology Five (PSY-5) facet subscale