ll-left[

### Training RMSE = 57367.26
&lt;img src="figs/01-Predicting/unnamed-chunk-46-1.png" width="504" /&gt;


]

--

.pull-right[

### Testing RMSE = 53884.78
&lt;img src="figs/01-Predicting/lm-test-resid-1.png" width="504" /&gt;
]


---
name: holdout-handout
class: center, middle

old data `(x, y)` + model = fitted model

--

new data `(x)` + fitted model = predictions

--

new data `(y)` + predictions = metrics

---
class: middle, center

# Quiz

How much data should you set aside for testing?

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I