Analyze model diagnostic plots (e.g., residual, marginal model, QQ, and added variable plots) to assess quality of fit.

Free CAS MAS-I (Modern Actuarial Statistics I) lesson in Extended Linear Models. 15 min read, ~2,228 words.

Residuals vs fitted checks the mean structure: a curved smoother flags non-linearity, a funnel flags heteroskedasticity, and a flat band near zero is the target. QQ plot of standardized residuals flags non-normal errors: S-shape is heavy tails (kurtosis), banana is skew, off-line endpoints are individual outliers. Scale-location plot isolates non-constant...

What this lesson covers

• Content
• Example 1
• Example 2
• Common Mistakes
• Check Your Understanding
• Exam Shortcuts

Learning objectives

• C8

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