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Question 21967: A Cell-Constant Conditional Version Has the Same Expectation

On this page
  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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← Question derivation index · Original question batch

R0042-21967 · q-20261014-advance-20261109-r04-law-of-total-expectation-0067

Original question and givens

Use the complete normalized finite law masses=[1/26, 2/26, 23/26, 0/1], aligned values X=[16, 17, 19, 115] and complete disjoint partition=[[0, 1], [2, 3]] covering every atom. Values are integrable in this finite model. Cell order and atom order are retained; independence is not required. Conditional quotients require strictly positive cell mass. Give (conditional_values, tower_expectation, mean, equal, certificate).

  • G001 — Use the complete normalized finite law masses=[1/26, 2/26, 23/26, 0/1], aligned values X=[16, 17, 19, 115] and complete disjoint partition=[[0, 1], [2, 3]] covering every atom. Values are integrable in this finite model. Cell order and atom order are retained; independence is not required. Conditional quotients require strictly positive cell mass. Give (conditional_values, tower_expectation, mean, equal, certificate).

Definition and scope

Use the original question domain, assumptions and cited MKO definitions. This item has second-context mathematical and bilingual review, with the model, answer and every arithmetic step independently recomputed from the original parameters; the source question remains a candidate.

Step-by-step derivation

S001 · implies

Before

source operation=totalexp-tower-identity;original snapshot and mathematics retained

After

explicit ordered source output fields=[conditional_values, tower_expectation, mean, equal, certificate]

Conditions: none

Keep the original historical interface marker while listing ordered source fields without JavaScript.Tags are not additional evidence;fixed No markers retain their source claim scope.

Step identifiers and dependencies

Rule: source_ordered_interface_explicit_without_javascript · Uses: G001

S002 · calculation

Before

Total expectation complete original mass := sum(1/26, 1/13, 23/26, 0)

After

Total expectation complete original mass = 1

Conditions: none

Substitute the original roles,order and conditions term by term with exact arithmetic,not floating-point approximation.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S001

S003 · calculation

Before

Total expectation original atom0 weighted X := mul(1/26, 16)

After

Total expectation original atom0 weighted X = 8/13

Conditions: none

Substitute the original roles,order and conditions term by term with exact arithmetic,not floating-point approximation.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S002

S004 · calculation

Before

Total expectation original atom1 weighted X := mul(1/13, 17)

After

Total expectation original atom1 weighted X = 17/13

Conditions: none

Substitute the original roles,order and conditions term by term with exact arithmetic,not floating-point approximation.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S003

S005 · calculation

Before

Total expectation original atom2 weighted X := mul(23/26, 19)

After

Total expectation original atom2 weighted X = 437/26

Conditions: none

Substitute the original roles,order and conditions term by term with exact arithmetic,not floating-point approximation.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S004

S006 · calculation

Before

Total expectation original atom3 weighted X := mul(0, 115)

After

Total expectation original atom3 weighted X = 0

Conditions: none

Substitute the original roles,order and conditions term by term with exact arithmetic,not floating-point approximation.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S005

S007 · calculation

Before

Total expectation full original mean := sum(8/13, 17/13, 437/26, 0)

After

Total expectation full original mean = 487/26

Conditions: none

Substitute the original roles,order and conditions term by term with exact arithmetic,not floating-point approximation.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S006

S008 · implies

Before

ORIGINAL masses=[1/26, 1/13, 23/26, 0],SIGNED values X=[16, 17, 19, 115];ORIGINAL cell order=[[0, 1], [2, 3]]

After

flattened original atom labels=[0, 1, 2, 3] cover EVERY atom exactly ONCE including null atoms;total mass=1;integrable finite mean=487/26;NO independence premise

Conditions: none

The partition covers all original atoms,including null atoms,exactly once.Keep original cell order and source-normalized internal labels.X may be signed and is integrable in this finite model;independence is not required.

Step identifiers and dependencies

Rule: totalexp_same_law_complete_disjoint_partition_all_atoms · Uses: G001, S007

S009 · calculation

Before

Total expectation cell0 mass := sum(1/26, 1/13)

After

Total expectation cell0 mass = 3/26

Conditions: none

Substitute the original roles,order and conditions term by term with exact arithmetic,not floating-point approximation.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S008

S010 · calculation

Before

Total expectation cell0 numerator := sum(8/13, 17/13)

After

Total expectation cell0 numerator = 25/13

Conditions: none

Substitute the original roles,order and conditions term by term with exact arithmetic,not floating-point approximation.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S009

S011 · calculation

Before

Total expectation cell0 positive-mass conditional mean := div(25/13, 3/26)

After

Total expectation cell0 positive-mass conditional mean = 50/3

Conditions: none

Substitute the original roles,order and conditions term by term with exact arithmetic,not floating-point approximation.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S010

S012 · implies

Before

ORIGINAL cell index=0,atom labels=[0, 1];mass=3/26;weighted numerator=25/13

After

conditional quotient=50/3;positive denominator qualifies division

Conditions: none

Divide only for positive cell mass.In a null cell,all nonnegative atom masses are0,so the numerator is0 but0/0 remains undefined.Keep null rather than an asserted quotient0,including empty cells.

Step identifiers and dependencies

Rule: totalexp_cell_quotient_positive_mass_only_null_preserved · Uses: G001, S011

S013 · calculation

Before

Total expectation cell1 mass := sum(23/26, 0)

After

Total expectation cell1 mass = 23/26

Conditions: none

Substitute the original roles,order and conditions term by term with exact arithmetic,not floating-point approximation.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S012

S014 · calculation

Before

Total expectation cell1 numerator := sum(437/26, 0)

After

Total expectation cell1 numerator = 437/26

Conditions: none

Substitute the original roles,order and conditions term by term with exact arithmetic,not floating-point approximation.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S013

S015 · calculation

Before

Total expectation cell1 positive-mass conditional mean := div(437/26, 23/26)

After

Total expectation cell1 positive-mass conditional mean = 19

Conditions: none

Substitute the original roles,order and conditions term by term with exact arithmetic,not floating-point approximation.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S014

S016 · implies

Before

ORIGINAL cell index=1,atom labels=[2, 3];mass=23/26;weighted numerator=437/26

After

conditional quotient=19;positive denominator qualifies division

Conditions: none

Divide only for positive cell mass.In a null cell,all nonnegative atom masses are0,so the numerator is0 but0/0 remains undefined.Keep null rather than an asserted quotient0,including empty cells.

Step identifiers and dependencies

Rule: totalexp_cell_quotient_positive_mass_only_null_preserved · Uses: G001, S015

S017 · calculation

Before

Total expectation positive cell0 weighted mean := mul(3/26, 50/3)

After

Total expectation positive cell0 weighted mean = 25/13

Conditions: none

Substitute the original roles,order and conditions term by term with exact arithmetic,not floating-point approximation.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S016

S018 · calculation

Before

Total expectation positive cell1 weighted mean := mul(23/26, 19)

After

Total expectation positive cell1 weighted mean = 437/26

Conditions: none

Substitute the original roles,order and conditions term by term with exact arithmetic,not floating-point approximation.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S017

S019 · calculation

Before

Total expectation sum positive-cell weighted means := sum(25/13, 437/26)

After

Total expectation sum positive-cell weighted means = 487/26

Conditions: none

Substitute the original roles,order and conditions term by term with exact arithmetic,not floating-point approximation.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S018

S020 · implies

Before

ALL original cell rows[index,atoms,mass,conditional_or_null,numerator]=[[0, [0, 1], 3/26, 50/3, 25/13], [1, [2, 3], 23/26, 19, 437/26]]

After

positive-cell weighted sum=487/26;ORIGINAL global mean=487/26;equal=Yes;disjoint complete cells regroup EVERY original p_i*X_i exactly ONCE,null contributions0

Conditions: none

Each positive mass times its conditional mean recovers its numerator;null cells contribute0.Disjoint complete cells then regroup every original weighted term exactly once.This proves the finite identity,not an unweighted average or an accidental numerical equality.

Step identifiers and dependencies

Rule: totalexp_regroup_complete_partition_general_identity · Uses: G001, S019

S021 · calculation

Before

Total expectation tower atom0 weighted conditional version := mul(1/26, 50/3)

After

Total expectation tower atom0 weighted conditional version = 25/39

Conditions: none

Substitute the original roles,order and conditions term by term with exact arithmetic,not floating-point approximation.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S020

S022 · calculation

Before

Total expectation tower atom1 weighted conditional version := mul(1/13, 50/3)

After

Total expectation tower atom1 weighted conditional version = 50/39

Conditions: none

Substitute the original roles,order and conditions term by term with exact arithmetic,not floating-point approximation.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S021

S023 · calculation

Before

Total expectation tower atom2 weighted conditional version := mul(23/26, 19)

After

Total expectation tower atom2 weighted conditional version = 437/26

Conditions: none

Substitute the original roles,order and conditions term by term with exact arithmetic,not floating-point approximation.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S022

S024 · calculation

Before

Total expectation tower atom3 weighted conditional version := mul(0, 19)

After

Total expectation tower atom3 weighted conditional version = 0

Conditions: none

Substitute the original roles,order and conditions term by term with exact arithmetic,not floating-point approximation.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S023

S025 · calculation

Before

Total expectation full tower expectation := sum(25/39, 50/39, 437/26, 0)

After

Total expectation full tower expectation = 487/26

Conditions: none

Substitute the original roles,order and conditions term by term with exact arithmetic,not floating-point approximation.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S024

S026 · implies

Before

ORIGINAL atom-order conditional version=[50/3, 50/3, 19, 19];ORIGINAL cells=[[0, 1], [2, 3]]

After

version constant on each cell,so measurable for sigma(partition);each cell integral equals original X cell integral;null-cell version CHOSEN0,not quotient;E(E(X|G))=487/26=E(X)=487/26

Conditions: none

Cell-constant values are measurable for the sigma-algebra generated by the partition.Cellwise integral identities extend to its finite cell unions,establishing a conditional-expectation version.On null cells0 is chosen,not a unique quotient.Weight by the original atom masses to obtain the tower identity.

Step identifiers and dependencies

Rule: totalexp_conditional_version_cell_measurability_and_tower · Uses: G001, S025

Reverse checks

  • S026 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
  • S025 · premise_and_result_audit — Recompute Total expectation full tower expectation with exact rational arithmetic, not rounded decimals.
  • S024 · premise_and_result_audit — Recompute Total expectation tower atom3 weighted conditional version with exact rational arithmetic, not rounded decimals.
  • S023 · premise_and_result_audit — Recompute Total expectation tower atom2 weighted conditional version with exact rational arithmetic, not rounded decimals.
  • S022 · premise_and_result_audit — Recompute Total expectation tower atom1 weighted conditional version with exact rational arithmetic, not rounded decimals.
  • S021 · premise_and_result_audit — Recompute Total expectation tower atom0 weighted conditional version with exact rational arithmetic, not rounded decimals.
  • S020 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
  • S019 · premise_and_result_audit — Recompute Total expectation sum positive-cell weighted means with exact rational arithmetic, not rounded decimals.
  • S018 · premise_and_result_audit — Recompute Total expectation positive cell1 weighted mean with exact rational arithmetic, not rounded decimals.
  • S017 · premise_and_result_audit — Recompute Total expectation positive cell0 weighted mean with exact rational arithmetic, not rounded decimals.
  • S016 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
  • S015 · premise_and_result_audit — Recompute Total expectation cell1 positive-mass conditional mean with exact rational arithmetic, not rounded decimals.
  • S014 · premise_and_result_audit — Recompute Total expectation cell1 numerator with exact rational arithmetic, not rounded decimals.
  • S013 · premise_and_result_audit — Recompute Total expectation cell1 mass with exact rational arithmetic, not rounded decimals.
  • S012 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
  • S011 · premise_and_result_audit — Recompute Total expectation cell0 positive-mass conditional mean with exact rational arithmetic, not rounded decimals.
  • S010 · premise_and_result_audit — Recompute Total expectation cell0 numerator with exact rational arithmetic, not rounded decimals.
  • S009 · premise_and_result_audit — Recompute Total expectation cell0 mass with exact rational arithmetic, not rounded decimals.
  • S008 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
  • S007 · premise_and_result_audit — Recompute Total expectation full original mean with exact rational arithmetic, not rounded decimals.
  • S006 · premise_and_result_audit — Recompute Total expectation original atom3 weighted X with exact rational arithmetic, not rounded decimals.
  • S005 · premise_and_result_audit — Recompute Total expectation original atom2 weighted X with exact rational arithmetic, not rounded decimals.
  • S004 · premise_and_result_audit — Recompute Total expectation original atom1 weighted X with exact rational arithmetic, not rounded decimals.
  • S003 · premise_and_result_audit — Recompute Total expectation original atom0 weighted X with exact rational arithmetic, not rounded decimals.
  • S002 · premise_and_result_audit — Recompute Total expectation complete original mass with exact rational arithmetic, not rounded decimals.
  • S001 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.

Result

([50/3, 50/3, 19, 19], 487/26, 487/26, Yes, conditional_expectation_constant_on_partition_cells)

The full substitutions and premise checks give the original answer; source identity,format and status are unchanged.

This question review and source binding

Review date: 2026-10-26

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: b028a12b5b3950519dfc2eeb9540e2ca38150e895afae5955770fec58fd48f05
  • candidate record SHA-256: bef788c3adf1082fb1de57a849e5745a3c6cf87c2a4cc0783df2afa0d694d011
  • semantic review receipt SHA-256: dd44555041dfbb6fe9936aa00b9a5f8c5982c2784ef61dd0cbd5d1a303a49c1a
  • question-first witness SHA-256: 9a6011263f6ac53b9a1fd57addf2f3e2f6088b54802c539f332d689480dc2d17
  • Lean: NOT_RUN · human review: NOT_PERFORMED
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