suggesting-remedies

• Trimming, raising ATO_THRESHOLD, or any sample restriction by propensity changes the estimand from the ATE to the ATO (at the chosen threshold). Never suggest "trim the ATE" or an "ATE trimming threshold" — those are contradictions. Suggest switching the estimand to ATO instead, and call out the estimand change explicitly.

Covariate Balance

• A failure means treatment and control units differ systematically in at least one confounder.
• Most likely affects the ATE — not every population covariate profile is well-represented in all treatment levels.
• Remedies: switch the estimand to ATT or ATO; raise ATO_THRESHOLD above 0.1 to trim extreme propensities; manually trim units with extreme values of the problematic covariates.
• Note in the report that all three remedies change the estimand away from the ATE.

Overlap

• A warning means many units have propensity scores near 0 or 1 (near-deterministic assignment).
• Not a hard fail — the estimator stays consistent — but extreme inverse weights cause instability and make counterfactuals depend on a few observations.
• Remedies: switch the estimand to ATT or ATO; trim by raising ATO_THRESHOLD. Note that trimming changes the estimand to the ATO at the chosen threshold.

Placebo

• A warning means a placebo outcome — known to be unaffected by treatment — has a statistically significant effect after adjustment.
• Not disqualifying: the placebo outcome is already controlled for in the actual analysis.
• The report MUST state that a placebo failure signals (a) high sensitivity of the results to a single confounder, and (b) likely residual confounding from variables the model has not captured.
• Primary remedy (MUST appear in suggestions whenever placebo warns): find and add covariates that explain the placebo outcome. These are the variables most likely driving the residual confounding. Identify candidates by training a model with the placebo as the target and inspecting which existing covariates have the highest feature importance — then add covariates that capture the same signal as those drivers.
• If the spec's covariate set already exhausts what's available in the dataset (e.g., the eval uses every x_* column), the report MUST explicitly state that the dataset may be insufficient for a credible analysis. Do not silently fall through to model-flexibility remedies.
• Propensity / outcome model flexibility (see Propensity model below) is a secondary remedy for placebo failures — list it only after the covariate-set remedy or the dataset-insufficiency note, never as the headline placebo response.

Propensity model

• Covariate balance failures and placebo warnings often indicate the propensity model is misspecified — it isn't capturing the true treatment-assignment process.
• Remedies: enable AUGMENT_CONTINUOUS_COVARIATES to add polynomial and bin-encoded versions of continuous features; switch to a more flexible propensity learner (e.g., gradient-boosted or deeper trees).
• These remedies do not change the estimand.
• If the propensity learner is already a flexible nonlinear model (e.g., XGBoost / LightGBM with sufficient depth and trees), augmentation is less likely to help — prefer adding more covariates, or accept that some confounding may be unobserved.