Using the 1983 norms for the MMPI: code type frequencies in four clinical samples

Area of Science:

• Psychological assessment
• Psychometrics
• Clinical psychology

Background:

• The Minnesota Multiphasic Personality Inventory (MMPI) is a widely used psychometric tool.
• Original MMPI norms may not accurately reflect current adult populations.
• Outdated norms can affect the validity of psychological assessments.

Purpose of the Study:

• To develop updated normative data for the MMPI based on a contemporary adult sample.
• To create new scoring procedures that yield normalized T scores.
• To enhance the interpretability and meaningfulness of MMPI results.

Main Methods:

• Collected MMPI responses from a large, random sample of midwestern adults (18-99 years old) without handicapping conditions.
• Developed sex-specific normative tables reflecting the general adult population.
• Created age-adjusted normative tables, separate for each sex.
• Implemented normalized T score transformations, replacing traditional linear transformations.

Main Results:

• MMPI response patterns from the contemporary sample significantly differed from original norms.
• New normative tables were established for general population comparisons and age-based adjustments.
• Normalized T scores replaced traditional scoring, accounting for raw score distribution skewness.
• Changes were observed at item, scale, and frequency levels of 1- and 2-point codes.

Conclusions:

• Updated MMPI norms based on contemporary data improve interpretive accuracy.
• New scoring procedures and normative tables enhance the meaningfulness of MMPI assessments.
• These revisions are crucial for valid psychological evaluations in current populations.