#validity

Establish psychometric properties of research instruments. Reliability assessment: 1. Internal consistency: Cronbach's α > 0.70 for research, > 0.90 for clinical decisions. 2. Test-retest: correlation between administrations 2-4 weeks apart (r > 0.80). 3. Inter-rater reliability: agreement between observers (ICC > 0.75, κ > 0.60). 4. Split-half: correlation between odd/even items, Spearman-Brown correction. Validity assessment: 1. Face validity: instrument appears to measure what it claims. 2. Content validity: expert panel review of item relevance (I-CVI > 0.78). 3. Construct validity: factor analysis confirms hypothesized structure. 4. Criterion validity: concurrent (correlates with gold standard) and predictive (predicts future outcomes). Advanced techniques: 1. Item Response Theory (IRT) for item-level analysis. 2. Generalizability theory for multiple sources of error. 3. Structural equation modeling for latent constructs. Report all reliability and validity evidence in methods section.