f .display[testing set] is small, 
performance metrics may be unreliable

--

If .display[training set] is small, model fit may be poor

---
class: middle, center, inverse

# Stratified sampling



---

&lt;img src="figs/01-Predicting/unnamed-chunk-48-1.png" width="504" style="display: block; margin: auto;" /&gt;

---

&lt;img src="figs/01-Predicting/unnamed-chunk-49-1.png" width="504" style="display: block; margin: auto;" /&gt;

---

&lt;img src="figs/01-Predicting/unnamed-chunk-50-1.png" width="504" style