docs: ITS sensitivity walkthrough (#788)

[drbenvincent]

Closes #788. Delivers the focused ITS sensitivity walkthrough requested as a follow-up to #749, scoped under #785.

Summary

docs/source/notebooks/its_post_intervention_analysis.ipynb (commit 10d2210)

• Rewrite the fixed-period ITS notebook opening around a concrete marketing-campaign question and add a clearer reader roadmap.
• Streamline the persistence walkthrough so the main results and sensitivity sections build on each other instead of repeating the same ideas.
• Reframe the placebo and persistence checks around learner-facing questions, then end with takeaways and a reflection prompt.
• Adds a worked Pipeline example combining the default PlaceboInTime check (via cp.SensitivityAnalysis.default_for(cp.InterruptedTimeSeries)) with a custom PersistenceCheck, plus a "What to do when a check looks weak" interpretation section.

Cross-linking polish (commit babdd2a)

• docs/source/notebooks/sensitivity_checks.md: add the walkthrough under both PlaceboInTime and PersistenceCheck in the "Where examples already exist" list, plus the closing :::{seealso} block.
• docs/source/notebooks/its_pymc.ipynb: add a closing "Going further: sensitivity checks" section pointing readers to the central guide and the new walkthrough.

Scope decision

After discussion on #788, we deliberately did not propagate the full sensitivity walkthrough to every ITS variant (its_pymc, its_covid, its_lift_test, its_pymc_comparative, piecewise_its_pymc, its_skl). Reasons:

• Avoid the "duplicated check boilerplate" anti-pattern called out in Expand docs coverage for pipeline sensitivity checks #785.
• Several variants (notably its_skl.ipynb) can't run the PyMC-only checks at all.
• A single canonical walkthrough plus discoverable links from the central guide and its_pymc.ipynb covers the use case without diluting the pedagogy of each method-specific notebook.

Test plan

• prek run --all-files
• make html
• its_post_intervention_analysis.ipynb executed end-to-end in the CausalPy env
• its_pymc.ipynb re-executed end-to-end in the CausalPy env so committed outputs reflect the new "Going further" section
• CI green on this PR (note: check-environment-yml failure is an unrelated upstream pyproject2conda regression, fixed by ci: pin pyproject2conda==0.22.1 to work around 0.23.0 regression #878)
• RTD preview spot-check: notebooks/its_post_intervention_analysis.html shows the new pipeline + persistence narrative; notebooks/its_pymc.html ends with the "Going further" seealso block; notebooks/sensitivity_checks.html lists the walkthrough under PlaceboInTime and PersistenceCheck

[review-notebook-app]

Check out this pull request on 

See visual diffs & provide feedback on Jupyter Notebooks.

---

Powered by ReviewNB

[drbenvincent]

TODO

• Add plot output for PlaceboInTime results
• Add plot output for PersistenceCheck results

I believe this plot functionality is being worked on in PR #819

[read-the-docs-community]

Documentation build overview

📚 causalpy | 🛠️ Build #32485220 | 📁 Comparing 4c023ef against latest (deb8774)

  🔍 Preview build  

4 files changed

± 404.html
± notebooks/its_post_intervention_analysis.html
± notebooks/its_pymc.html
± notebooks/sensitivity_checks.html

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.59%. Comparing base (2ff6b7b) to head (4c023ef).
⚠️ Report is 48 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #821   +/-   ##
=======================================
  Coverage   94.59%   94.59%           
=======================================
  Files          80       80           
  Lines       12764    12764           
  Branches      770      770           
=======================================
  Hits        12074    12074           
  Misses        486      486           
  Partials      204      204           

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[drbenvincent]

Note: this PR is not a duplicate of #806. Both are follow-ups from #749, but they target different methods and different notebooks:

• docs: ITS sensitivity walkthrough (#788) #821 (this PR) → ITS sensitivity walkthrough (its_post_intervention_analysis.ipynb), addresses Docs: Add ITS sensitivity checks walkthrough (follow-up #749) #788
• add walkthrough and result interpretation #806 → Staggered DiD sensitivity walkthrough (staggered_did_pymc.ipynb), addresses Docs: Add Staggered DiD sensitivity checks walkthrough (follow-up #749) #791

No overlap in files or content.

[drbenvincent]

Failing CI check unrelated to this PR. Fix in flight #878

[drbenvincent]

Heads-up for reviewers: the failing check-environment-yml job is not caused by this PR. It's an upstream regression in pyproject2conda 0.23.0 that hits all currently-open PRs; #878 pins it back to 0.22.1 and will resolve it once merged + this branch is updated from main.

[review-notebook-app]

View / edit / reply to this conversation on ReviewNB

cetagostini commented on 2026-05-02T02:54:35Z
----------------------------------------------------------------

Line #5.        formula="y ~ 1 + t + C(month, levels=[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12])",

Worth explain the formula, mostly the levels part. You can have people not familiar, at least say what numbers represent other parts are more intuitive.

[review-notebook-app]

View / edit / reply to this conversation on ReviewNB

cetagostini commented on 2026-05-02T02:54:36Z
----------------------------------------------------------------

During the during intervention?

[review-notebook-app]

View / edit / reply to this conversation on ReviewNB

cetagostini commented on 2026-05-02T02:54:37Z
----------------------------------------------------------------

I think this conclusion will change given the updates and corrections in the class, during my PR #826.

[review-notebook-app]

View / edit / reply to this conversation on ReviewNB

cetagostini commented on 2026-05-02T02:54:37Z
----------------------------------------------------------------

During the persistent check are we checking all the remaining time series or the N weeks defined above? This was not very clear to me during the reading.

[review-notebook-app]

View / edit / reply to this conversation on ReviewNB

cetagostini commented on 2026-05-02T02:54:38Z
----------------------------------------------------------------

Good, I like it