#sem

Optimize PPC campaigns for ROI. Strategy: 1. Keyword match types (exact, phrase, broad). 2. Negative keywords to reduce waste. 3. Ad group structure by theme. 4. Compelling ad copy with CTAs. 5. Landing page relevance and quality score. 6. Bid adjustments by device, location, time. 7. Ad extensions (sitelinks, callouts). 8. Conversion tracking and attribution. Use automated bidding strategies and A/B test ads continuously.

Test complex theoretical models using SEM. Model specification: 1. Draw path diagram showing hypothesized relationships. 2. Identify endogenous (dependent) and exogenous (independent) variables. 3. Specify direct and indirect paths. 4. Include error terms for endogenous variables. Analysis in R lavaan or SPSS AMOS: 1. Measurement model: confirmatory factor analysis for latent constructs. 2. Structural model: test path relationships. 3. Model identification: degrees of freedom ≥ 0 for identified model. Sample size: minimum 200 observations, 10-20 per parameter. Model fit assessment: 1. Chi-square test (non-significant preferred but sensitive to sample size). 2. Comparative Fit Index (CFI > 0.95). 3. Root Mean Square Error of Approximation (RMSEA < 0.08). 4. Standardized Root Mean Square Residual (SRMR < 0.08). Modification indices suggest model improvements, but use theory-driven changes only.