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Question 21994: Null Cells Retain Undefined Quotients and Zero Weighted Contributions

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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R0042-21994 · q-20261014-advance-20261109-r04-law-of-total-expectation-0094

Original question and givens

Use the complete normalized finite law masses=[1/28, 2/28, 25/28, 0/1], aligned values X=[18, 19, 21, 117] 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 (cell_rows, positive_cell_weighted_sum, mean, equal, null_cell_division_claim, boundary).

  • G001 — Use the complete normalized finite law masses=[1/28, 2/28, 25/28, 0/1], aligned values X=[18, 19, 21, 117] 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 (cell_rows, positive_cell_weighted_sum, mean, equal, null_cell_division_claim, boundary).

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-zero-mass-boundary;original snapshot and mathematics retained

After

explicit ordered source output fields=[cell_rows, positive_cell_weighted_sum, mean, equal, null_cell_division_claim, boundary]

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(1/28, 1/14, 25/28, 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(1/28, 18)

After

Total expectation original atom0 weighted X = 9/14

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(1/14, 19)

After

Total expectation original atom1 weighted X = 19/14

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(25/28, 21)

After

Total expectation original atom2 weighted X = 75/4

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, 117)

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(9/14, 19/14, 75/4, 0)

After

Total expectation full original mean = 83/4

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=[1/28, 1/14, 25/28, 0],SIGNED values X=[18, 19, 21, 117];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=83/4;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(1/28, 1/14, 25/28)

After

Total expectation cell0 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, S008

S010 · calculation

Before

Total expectation cell0 numerator := sum(9/14, 19/14, 75/4)

After

Total expectation cell0 numerator = 83/4

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(83/4, 1)

After

Total expectation cell0 positive-mass conditional mean = 83/4

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, 2];mass=1;weighted numerator=83/4

After

conditional quotient=83/4;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(0)

After

Total expectation cell1 mass = 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, S012

S014 · calculation

Before

Total expectation cell1 numerator := sum(0)

After

Total expectation cell1 numerator = 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, S013

S015 · implies

Before

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

After

conditional quotient=null;null cell:every nonnegative atom mass is0,numerator0;NO division performed

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, S014

S016 · calculation

Before

Total expectation positive cell0 weighted mean := mul(1, 83/4)

After

Total expectation positive cell0 weighted mean = 83/4

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, S015

S017 · calculation

Before

Total expectation sum positive-cell weighted means := sum(83/4)

After

Total expectation sum positive-cell weighted means = 83/4

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 · implies

Before

ALL original cell rows[index,atoms,mass,conditional_or_null,numerator]=[[0, [0, 1, 2], 1, 83/4, 83/4], [1, [3], 0, null, 0]]

After

positive-cell weighted sum=83/4;ORIGINAL global mean=83/4;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, S017

S019 · implies

Before

ACTUAL null cells=[1];positive weighted sum=83/4;mean=83/4

After

null_cell_division_claim fixed No;undefined cell quotients remain null,while the weighted total-expectation identity still holds

Conditions: none

The final No rejects null-cell division,not the identity.A conditional-expectation version may choose a value on a null cell,but not as a uniquely computed0/0 quotient.

Step identifiers and dependencies

Rule: totalexp_null_division_nonclaim_not_tower_failure · Uses: G001, S018

Reverse checks

  • S019 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
  • S018 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
  • S017 · premise_and_result_audit — Recompute Total expectation sum positive-cell weighted means with exact rational arithmetic, not rounded decimals.
  • S016 · premise_and_result_audit — Recompute Total expectation positive cell0 weighted mean with exact rational arithmetic, not rounded decimals.
  • S015 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
  • 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

([[0, 1, 83/4], [1, 0, null]], 83/4, 83/4, Yes, No, zero_mass_conditional_mean_not_divided_and_weighted_contribution_zero)

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: f1f1682fb791ff7ab0e745c6c4f565642b2b808d70c2b72857e1a38f68c78964
  • candidate record SHA-256: ec5a795eaa60ade838ed55eb065f9bb4809dae03159d671c3d4b210775a806d8
  • semantic review receipt SHA-256: dd44555041dfbb6fe9936aa00b9a5f8c5982c2784ef61dd0cbd5d1a303a49c1a
  • question-first witness SHA-256: 9a6011263f6ac53b9a1fd57addf2f3e2f6088b54802c539f332d689480dc2d17
  • Lean: NOT_RUN · human review: NOT_PERFORMED
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