# Contract — F1-conf-04
**Question:** Summarise the property-sales export `data/sales.csv` and reconcile it with provider control totals in `data/metadata.json`.
**Estimands:** (1) number of records readable unambiguously (n_valid = n_analysed); (2) sum and (3) mean of price_cad over them; (4) median of price_cad/area_m2 over them; (5) reconciliation: control count vs valid count (n_unreadable = control − valid) and control sum vs valid sum (implied unreadable sum). Descriptive quantities over a finite file — meaningful assuming control totals refer to the same table and that readable rows are correct as recorded. Mean/median refer to readable records only; they generalise to the full table only if unreadable records are missing-at-random.
**Outputs:** out/results.json (task_id, n_records_control, n_valid_records, n_unreadable_records, n_analysed, sum_price_control, sum_price_valid, sum_price_unreadable_implied, mean_price_valid, median_price_per_m2_valid, feasibility, feasibility_reason, data_issues, n_input_rows{"sales.csv"}, random_seed); out/analytic.csv (sale_id, municipality, sale_date, price_cad, area_m2; n_analysed rows); out/exclusions.csv (step, rule, n_before, n_after, n_removed, rationale; chained); out/report.md (Question; Data and exclusions; Method; Results; Uncertainty; Limitations and open issues); out/analysis.py; out/claims.json.
**Availability rules:** only data/ files; no reconstruction/imputation/guessing of unreadable records; feasibility "complete" only if every control record enters analysis, else "partial" with exact count and reason.
**Invalidity:** fabricating content for corrupted rows; using anything outside data/; mismatched counts in ledger; claiming "complete" when rows are lost.