Question 50
For Westhaven Marketplace, the engineer must verify a remediation with measured evidence, not just a deployment claim. The original failure was: A retailer wants separate forecasts for hundreds of stores but inadvertently aggregates all locations into one time series. Which independently observable result best verifies that the remediation works?
Explanation
Correct Answer
Forecasts retain store IDs and independent store-level holdout errors are available for inspection. This controlled observation specifically validates the proposed remedy: Create a multi-series BigQuery ML forecast keyed by store identity and the event date rather than pooling locations into one series. It addresses the documented failure at Westhaven Marketplace: A retailer wants separate forecasts for hundreds of stores but inadvertently aggregates all locations into one time series.
Incorrect Answers
A reviewer can reproduce a feature contribution for a selected prediction and the explanation report does not claim causal proof. This is evidence for a different corrective change: Use supported BigQuery ML model-evaluation and explanation functions at the appropriate global or local scope and distinguish contribution from causation. That other change addresses: A customer support team cannot explain why an SQL-trained BigQuery ML model prioritizes a prediction and treats a coefficient printout as a complete local explanation. It does not validate the specific Westhaven Marketplace remediation for: A retailer wants separate forecasts for hundreds of stores but inadvertently aggregates all locations into one time series. The necessary check instead is: Forecasts retain store IDs and independent store-level holdout errors are available for inspection.
A controlled dataset with nulls produces complete training rows and a per-column missingness audit without label leakage. This is evidence for a different corrective change: Define and fit an explicit BigQuery ML missing-value imputation strategy and track the percentage of imputed records. That other change addresses: A product-cost prediction query silently drops rows with missing numeric features, biasing the downstream training sample. It does not validate the specific Westhaven Marketplace remediation for: A retailer wants separate forecasts for hundreds of stores but inadvertently aggregates all locations into one time series. The necessary check instead is: Forecasts retain store IDs and independent store-level holdout errors are available for inspection.
Held-out user-item recommendations rank relevant items more effectively than a non-personalized popularity baseline. This is evidence for a different corrective change: Use a BigQuery ML recommendation approach such as matrix factorization with appropriate user, item, and interaction data. That other change addresses: A media platform seeks implicit user-item recommendations but trains an ordinary numeric sales regression with user IDs as magnitudes. It does not validate the specific Westhaven Marketplace remediation for: A retailer wants separate forecasts for hundreds of stores but inadvertently aggregates all locations into one time series. The necessary check instead is: Forecasts retain store IDs and independent store-level holdout errors are available for inspection.