Exam Strategy
Readiness Check
You are ready when you can:
- Fit linear, quadratic, and exponential models to a table or scatterplot.
- Compute and interpret residuals.
- Read a residual plot for pattern vs random scatter.
- Defend a model choice with context and validation evidence.
On the AP Exam
- MCQ: identify best model type, read residual plot, interpret error direction.
- FRQ: construct competing models, residual analysis, justify choice.
- Skills: 2.A identify from representations; 3.C support conclusions with rationale/data.
Tactics
1. Quick screen: constant differences $\rightarrow$ linear; constant ratios $\rightarrow$ exponential; one bend $\rightarrow$ quadratic candidate. 2. Always check residuals for the finalist models. 3. Context beats algebra: inventory safety, drug dosing, structural limits. 4. Residual plot with clear curve/U/fan $\Rightarrow$ model mismatch. 5. State error direction: predicted $-$ actual (or define your sign convention clearly).
Common Traps
- Exponential on nearly linear data.
- Quadratic extrapolation beyond observed window.
- Claiming "good fit" with patterned residuals.
- Ignoring which direction of error is costly.
Quick Checklist
- [ ] At least two competing models considered
- [ ] Residual plot examined
- [ ] Context reason stated
- [ ] Error direction linked to scenario if asked