Optimizing the length, width, and balance of a personality scale: How do internal characteristics affect external...

Area of Science:

• Psychological Assessment
• Personality Psychology

Background:

• External validity is crucial for personality assessment, evaluating how well scales predict real-world behaviors and outcomes.
• Internal scale characteristics, including length, width, and balance, may influence this predictive accuracy.

Purpose of the Study:

• To investigate the impact of personality trait scale characteristics (length, width, balance) on external validity.
• To provide practical recommendations for constructing more effective personality assessment tools.

Main Methods:

• Utilized the Big Five Inventory-2 (BFI-2) item pool to create varied trait scale versions.
• Manipulated scale length, content breadth (width), and item keying (balance).
• Assessed participants on self- and peer-reported criteria to measure external validity.

Main Results:

• Longer scales demonstrated greater external validity, with an optimal range of 6-9 items.
• Broader scales showed more consistent, slightly stronger associations with validity criteria compared to narrow scales.
• Balanced scales (equal positive/negative items) effectively mitigated acquiescence bias, preventing inflated or suppressed validity correlations.

Conclusions:

• Scale length, width, and balance significantly affect external validity in personality assessment.
• Recommendations include using moderately long (6-9 items), broad, and balanced scales for improved predictive accuracy.
• Findings offer practical guidance for enhancing the design and application of personality measures.