FA-12636 / Survey sampling estimators / Open access
Deduplicating repeated PPS draws changes the estimator · case 01
Deduplicating repeated PPS draws changes the estimator.
ROOT CAUSE
Repeated with-replacement draws are collapsed before Hansen-Hurwitz estimation.
THE FAILURE
Repeated with-replacement draws are collapsed before Hansen-Hurwitz estimation.
Unsuccessful approach: Keeping occurrences but dividing by number of unique units still inflates the result.
Case contract
draws are (unit identifier,value,positive draw probability); repeated unit entries have identical value and probability. Return Hansen-Hurwitz population total rounded to eight decimals, or None for no draws.
Why this case matters
A deterministic survey-design model isolates this sampling contract before it is embedded in a larger estimation pipeline.
1 / The failure
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
N = 1
observations = []
def solve(draws):
unique={u:(y,p) for u,y,p in draws}
return round(sum(y/p for y,p in unique.values())/len(unique),8) if unique else None
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('unequal repeat multiplicity',solve([('a',N,0.5),('a',N,0.5),('b',4*N,0.5)]),4*N)
check('same unit twice',solve([('a',N,0.25),('a',N,0.25)]),4*N)
check('single draw',solve([('a',N,0.25)]),4*N)
check('different unique draws',solve([('a',N,0.5),('b',3*N,0.5)]),4*N)
check('zero valued draw counts',solve([('a',0,0.5),('a',0,0.5),('b',3*N,0.5)]),2*N)
check('no draws',solve([]),None)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
| Boundary fixture | Actual | Expected | Outcome |
|---|---|---|---|
| unequal repeat multiplicity | 5.0 | 4 | Failed |
| same unit twice | 4.0 | 4 | Passed |
| single draw | 4.0 | 4 | Passed |
| different unique draws | 4.0 | 4 | Passed |
| zero valued draw counts | 3.0 | 2 | Failed |
| no draws | None | None | Passed |
SHA-256 / 847223d69f92732110ef448f406bdb7a8d1e07d3e08bb5215716b891a9d7b548
2 / The unsuccessful fix
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
N = 1
observations = []
def solve(draws):
return round(sum(y/p for u,y,p in draws)/len({u for u,y,p in draws}),8) if draws else None
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('unequal repeat multiplicity',solve([('a',N,0.5),('a',N,0.5),('b',4*N,0.5)]),4*N)
check('same unit twice',solve([('a',N,0.25),('a',N,0.25)]),4*N)
check('single draw',solve([('a',N,0.25)]),4*N)
check('different unique draws',solve([('a',N,0.5),('b',3*N,0.5)]),4*N)
check('zero valued draw counts',solve([('a',0,0.5),('a',0,0.5),('b',3*N,0.5)]),2*N)
check('no draws',solve([]),None)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
| Boundary fixture | Actual | Expected | Outcome |
|---|---|---|---|
| unequal repeat multiplicity | 6.0 | 4 | Failed |
| same unit twice | 8.0 | 4 | Failed |
| single draw | 4.0 | 4 | Passed |
| different unique draws | 4.0 | 4 | Passed |
| zero valued draw counts | 3.0 | 2 | Failed |
| no draws | None | None | Passed |
SHA-256 / 6e4067782c70a048199eecf8cb1e202c64dd06810377bbf498432ca160a1ec20
HELD IN THE MEMBER ARCHIVE
The verified repair and its recorded checks are member-only.
This mechanism has 6 recorded checks per implementation. The open-access tier publishes the failure and the unsuccessful fix; the repaired source that passes every check, and the observations that prove it, are available to members.
Every case sharing this mechanism uses the same contract and the same repair, so this one record is held back for all of them.
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Sign in to the archive ↗Verification & scope
Controlled finite fixtures; not a general survey-analysis package. This reproducer isolates one failure mechanism. Results cover the supplied fixtures. Variants within a family share a test contract and should remain grouped when constructing evaluation splits. Related mechanisms with a shared evaluation_group must also remain together; these controlled models are not independent production incidents.
Observations recorded using Python 3.12.14 at 2026-09-29T14:38:58.792999+00:00.
Case digest / 26b33d996b4b2a777a17e357476201a618386b4a4892b3e898fa3e545d91e2fe