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Question 170: Retain Every Likelihood Maximizer before Discussing Uniqueness

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  1. Original question and givens
  2. Definition and scope
  3. Step-by-step derivation
  4. Reverse checks
  5. Result
  6. This question review and source binding

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P250-0170 · q-20261015-advance-20261116-r04-finite-maximum-likelihood-estimator-0045

Original question and givens

Use complete theta labels=[a19, b19], observations=[x19, y19] and aligned exact probability rows=[[[3, 4], [1, 4]], [[1, 4], [3, 4]]]. Each theta row is nonnegative and sums to1. Sort labels with their associated rows/columns, never independently. Observed label=x19. Give (observed, likelihood_rows, maximum_likelihood, argmax_parameters, unique_argmax, certificate).

  • G001 — Use complete theta labels=[a19, b19], observations=[x19, y19] and aligned exact probability rows=[[[3, 4], [1, 4]], [[1, 4], [3, 4]]]. Each theta row is nonnegative and sums to1. Sort labels with their associated rows/columns, never independently. Observed label=x19. Give (observed, likelihood_rows, maximum_likelihood, argmax_parameters, unique_argmax, certificate).

Definition and scope

Use complete finite parameter and observation carriers. Fix the observed column, retain the full argmax, and introduce no prior.

Step-by-step derivation

S001 · implies

Before

Θ=[a19, b19]; Ω=[x19, y19]

After

observed=x19, column=0

Conditions: none

Fix the observed outcome and compare its one probability column across parameter values.

Step identifiers and dependencies

Rule: fixed_observation · Uses: G001

S002 · calculation

Before

P_a19(Ω) := sum(3/4, 1/4)

After

P_a19(Ω) = 1

Conditions: none

First check that this parameter's row remains a normalized probability law.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S001

S003 · implies

Before

row for a19=[3/4, 1/4]

After

L(a19;x19)=P_a19(x19)=3/4

Conditions: none

Take the probability at the observed label in this row, without introducing a prior.

Step identifiers and dependencies

Rule: likelihood_lookup · Uses: G001, S002

S004 · calculation

Before

P_b19(Ω) := sum(1/4, 3/4)

After

P_b19(Ω) = 1

Conditions: none

First check that this parameter's row remains a normalized probability law.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S003

S005 · implies

Before

row for b19=[1/4, 3/4]

After

L(b19;x19)=P_b19(x19)=1/4

Conditions: none

Take the probability at the observed label in this row, without introducing a prior.

Step identifiers and dependencies

Rule: likelihood_lookup · Uses: G001, S004

S006 · implies

Before

L(a19;x19)=3/4, maximum=3/4

After

a19 ∈ argmax: Yes

Conditions: none

Include every parameter that attains the maximum, including ties after the first maximizer.

Step identifiers and dependencies

Rule: argmax_membership · Uses: G001, S005

S007 · implies

Before

L(b19;x19)=1/4, maximum=3/4

After

b19 ∈ argmax: No

Conditions: none

Include every parameter that attains the maximum, including ties after the first maximizer.

Step identifiers and dependencies

Rule: argmax_membership · Uses: G001, S006

S008 · implies

Before

argmax=[a19]

After

unique maximizing parameter: Yes

Conditions: none

Only a complete argmax with exactly one element has a unique maximizing parameter.

Step identifiers and dependencies

Rule: cardinality_one · Uses: G001, S007

S009 · implies

Before

finite normalized laws

After

MLE is not a posterior or an automatic quality certificate

Conditions: none

If all likelihoods at an observation are zero, every parameter still maximizes at 0; this computation does not imply unbiasedness or consistency.

Step identifiers and dependencies

Rule: scope_boundary · Uses: G001, S008

Reverse checks

  • S009 · premise_and_result_audit — Do not confuse a null observation column with an invalid all-zero probability-law row.
  • S008 · premise_and_result_audit — A fixed tie-breaker can select one output without making a multi-element argmax a singleton.
  • S007 · premise_and_result_audit — The maximum is a number; argmax is a set of parameters.
  • S006 · premise_and_result_audit — The maximum is a number; argmax is a set of parameters.
  • S005 · premise_and_result_audit — The value remains bound to the same parameter and observation.
  • S004 · premise_and_result_audit — Recompute P_b19(Ω) with exact rational arithmetic, not rounded decimals.
  • S003 · premise_and_result_audit — The value remains bound to the same parameter and observation.
  • S002 · premise_and_result_audit — Recompute P_a19(Ω) with exact rational arithmetic, not rounded decimals.
  • S001 · premise_and_result_audit — Do not confuse other observations in a row with other parameter values.

Result

(x19, [[a19, 3/4], [b19, 1/4]], 3/4, [a19], Yes, MLE_argmax_need_not_be_unique)

The maximum likelihood is 3/4; the complete argmax is [a19].

This question review and source binding

Review date: 2026-10-24

Original questions, answers, step expressions, numeric ASTs and historical records are retained. Source candidate labels remain historical and are not overwritten as formal proof.

Source hashes and review receipts
  • input commit: 0f7be61e2c22317a4075561dc822c87d881a50db
  • original question SHA-256: 52c6476c5e2838c270476747f56ac21d4e4558adcf2a51807fcdd83f2a58acb2
  • candidate record SHA-256: 1e45db084cba7a4d1ab74fe84e4281d0979794606aad8ba326b4ccc370008f26
  • semantic review receipt SHA-256: 4727d1bd957a9b7f6cadb7972ddb5ab80a31f5259dc5394c1dff2b71944ed36b
  • question-first witness SHA-256: 51e18649133238ac992229f6e16542a5f3af53ca73b2262ab0524508ea937dee
  • Lean: NOT_RUN · human review: NOT_PERFORMED
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