Page 6 of 8~112 min topic

Decision trees

Instrument the readiness decision tree

Page 6 adds signals that distinguish bad input from component failure in the readiness decision tree on hours × practice tests.

~14 min this pageTesting and observability

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Emit stage signals

Instrument the readiness decision tree on hours × practice tests so a run records enough structure to debug offline: counts, latency if relevant, pass/fail of held-out accuracy plus a tree text dump that mentions both features, and a stable stage name. Redact secrets and raw credentials from every event.

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Emit and assert

import json
print(json.dumps({'model':'DecisionTree','max_depth':2,'features':['hours','practice_tests'],'holdout_acc':1.0}))

Expected evidence: tree metrics JSON. Prefer JSON or structured text you can grep in CI over prose logs for decision-trees.

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Lock signals with a regression test

Turn one historical failure—especially overfit tree with max_depth unrestricted on tiny data—into a test that fails if the signal disappears for the readiness decision tree. Observability without a failing test is optional decoration; observability with a test is part of the decision-trees artifact.

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Lab notebook: signal schema

Draft a three-field event for the readiness decision tree: stage, ok, and one domain field derived from held-out accuracy plus a tree text dump that mentions both features. Add fixture_id or docs_version when content can change. Explicitly list fields that must never appear (tokens, passwords, raw prompts) because training on labels that embed sensitive attributes without documenting them is in scope for this lab.

Wire one assertion that fails if the readiness decision tree event is missing after a run. Observability that cannot fail a test will not survive contact with a busy decision-trees repository.

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Worked judgment

Imagine a teammate opens only your event stream after a bad deploy. Could they tell whether small hours/practice_tests readiness table with one holdout row was wrong, whether overfit tree with max_depth unrestricted on tiny data, or missing feature names in export returned, or whether training on labels that embed sensitive attributes without documenting them slipped through? If not, rename fields until those three stories are distinguishable.

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Why this stage matters for the readiness decision tree

At the testing and observability stage for decision-trees, the job is narrower than finishing a product demo. You are creating one progressive evidence piece about small hours/practice_tests readiness table with one holdout row that later pages inherit without redefining success. Keep that fixture small enough to inspect by hand, keep outputs copy-pasteable as text, and refuse to narrate this baseline as if it were a production SLA: majority-class accuracy on the holdout before fitting the tree.

For this page specifically, success looks like a structured event schema locked by a test while still centering the user decision to predict readiness with a path a human can read aloud. If you cannot point to a file, command, or assertion that proves that for the readiness decision tree, stay on this page instead of advancing.

Decision tree glossary

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Before you start

Why this matters

Write the single log line or metric event that would tell you whether a bad result came from input vs implementation for the readiness decision tree. If your line could not tell them apart, redesign it before coding.

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Page assessment

Answer from memory. Completion is saved from this evidence, not from opening the next page.

1. Can input faults be distinguished from component faults in the event?
2. Are secrets redacted from logs?
3. Is there a test that fails if the signal vanishes?
4. Does the event still reference the decision: predict readiness with a path a human can read aloud?

All responses are required.