Understanding how personality tests are constructed and validated helps you interpret results appropriately and choose quality instruments.
Test Construction
Item Development
Tests begin with items (questions or statements) designed to measure specific constructs. Good items:
- Clearly relate to the trait being measured
- Are understandable across different populations
- Avoid leading or biased wording
- Don't have obvious "right" answers
Response Formats
- Likert scales: Agreement from "strongly disagree" to "strongly agree"
- Forced choice: Choose between two options
- Semantic differential: Rate between opposing adjectives
- Frequency: How often behavior occurs
Psychometric Properties
Reliability
Consistency of measurement. Types include:
- Internal consistency: Do items measuring the same trait correlate?
- Test-retest: Do scores remain stable over time?
- Inter-rater: Do different raters agree? (for observer-rated measures)
Good tests have reliability coefficients above .70, preferably above .80.
Validity
Whether the test measures what it claims to. Types include:
- Content validity: Do items represent the full construct?
- Construct validity: Does it correlate with related measures and not with unrelated ones?
- Criterion validity: Does it predict relevant outcomes?
- Face validity: Does it appear to measure what it claims?
Common Issues
Response Biases
- Social desirability: Answering to look good
- Acquiescence: Tendency to agree regardless of content
- Extreme responding: Using only endpoints of scales
- Careless responding: Not reading items carefully
Self-Report Limitations
- Limited self-awareness
- Current mood affects responses
- Reference group effects (comparing to different standards)
- Motivation to present in certain ways
Interpreting Results
Norms
Scores are meaningful when compared to a reference group (norm sample). Ask:
- How large and representative is the norm sample?
- Is the norm sample appropriate for you?
- When were norms collected?
Standard Error
All measurements have error. A score of 50 with standard error of 5 means the "true" score is likely between 45-55. Small score differences may not be meaningful.
Evaluating Test Quality
Before trusting a test, consider:
- Is there a test manual with technical information?
- Has it been peer-reviewed and published?
- Are reliability and validity data available?
- Is the norm sample appropriate?
- What are its known limitations?
Ethical Considerations
- Tests should be used for intended purposes
- Results should be interpreted by qualified individuals
- Test-takers should understand how results will be used
- Cultural and individual differences must be considered
- No single test should be the sole basis for important decisions