CHAPTER 02 / 06 · TRAIN

Train. Test. Explain.

Machine learning Applied AI Engineering

A useful model starts with a baseline, separates learning from evaluation and makes mistakes easy to inspect.

THE QUESTION

Does the model improve on a simple rule outside its training examples?

FIG. 02 / THE DECISION FIELD EXAMPLE SYSTEM
Simple rule / first comparison

A basic rule sets the bar. More complexity only helps when the evidence improves.

02 / THE PROCESS

From idea
to evidence.

Three connected moves explain the subject and the work that makes it reviewable.

An evaluation report that includes failure cases.

  1. 01 / TRAIN

    Start with a baseline

    Define a simple comparison before training so improvement has a meaningful reference.

    WHAT YOU CAN SHOWBaseline result
  2. 02 / VALIDATE

    Protect the validation split

    Prepare features without letting information from held-out examples leak into training.

    WHAT YOU CAN SHOWDocumented split and features
  3. 03 / COMPARE

    Review what fails

    Look beyond one score to false positives, false negatives and cases near the boundary.

    WHAT YOU CAN SHOWEvaluation with failure cases

THE PRACTICE

Make the work
inspectable.

The example is a way to explore the idea. Real project evidence should include what was tried, what was observed and what remains uncertain.

01 / STARTMove through features, train and validation splits, leakage, baseline models and meaningful evaluation.
02 / DOCompare a simple baseline with a trained model.
03 / SHOWAn evaluation report that includes failure cases.

KEEP IN VIEW

What the visual
doesn’t prove.

The visual uses illustrative data. A smooth boundary alone does not prove that a model generalises.

ROLE CONNECTIONS

These directions use ideas from this subject within the Applied AI Engineering learning path.

INVESTIGATEData Scientist
ENGINEERML Engineer
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