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Question 31687: Expectation of a Sum on the Same Model

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

R0062-31687 · q-20261004-advance-20261005-r06-expectation-0062

Original question and givens

The nonempty finite sample space is S={0, 1, 2, 3}, with event family F=𝒫(S). The total function X:S→R has table {(0, -17), (1, -17), (2, -4), (3, 1010)}. In the displayed order of S, the nonnegative probability weights are [1/(20), 13/(20), 6/(20), 0/(20)], summing exactly to one. On the same S, Y has table {(0, -33), (1, -33), (2, -7), (3, 2021)}. Compute E[X+Y] exactly without introducing a separate independent model.

  • G001 — The nonempty finite sample space is S={0, 1, 2, 3}, with event family F=𝒫(S). The total function X:S→R has table {(0, -17), (1, -17), (2, -4), (3, 1010)}. In the displayed order of S, the nonnegative probability weights are [1/(20), 13/(20), 6/(20), 0/(20)], summing exactly to one. On the same S, Y has table {(0, -33), (1, -33), (2, -7), (3, 2021)}. Compute E[X+Y] exactly without introducing a separate independent model.

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 roles = [qf-expectation-same-model-sum, no-domain-field, sum_expectation, no-form-field]

After

derived = [[reduced_fraction_RETAIN1_STRING]]

Conditions: none

Check THIS bank interface:BASE equations use form/domain;BASE events/complement have no operation;factorials have no domain.ext18 uses local hyphens,other legacy operations underscores.Do not force every answer into a tuple or fraction.

Step identifiers and dependencies

Rule: R62_EXACT_source_keys_domain_operation_form_AND_output_types · Uses: G001

S002 · calculation

Before

Expectation ORIGINAL weight total through slot0 := sum(0, 1)

After

Expectation ORIGINAL weight total through slot0 = 1

Conditions: none

Use ORIGINAL operands and declared order for exact integer/rational arithmetic,not floats.Bounds are family-specific:do not revalidate derived values as RAW inputs or add blanket SAFE/n64 caps to BASE families.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S001

S003 · calculation

Before

Expectation ORIGINAL weight total through slot1 := sum(1, 13)

After

Expectation ORIGINAL weight total through slot1 = 14

Conditions: none

Use ORIGINAL operands and declared order for exact integer/rational arithmetic,not floats.Bounds are family-specific:do not revalidate derived values as RAW inputs or add blanket SAFE/n64 caps to BASE families.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S002

S004 · calculation

Before

Expectation ORIGINAL weight total through slot2 := sum(14, 6)

After

Expectation ORIGINAL weight total through slot2 = 20

Conditions: none

Use ORIGINAL operands and declared order for exact integer/rational arithmetic,not floats.Bounds are family-specific:do not revalidate derived values as RAW inputs or add blanket SAFE/n64 caps to BASE families.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S003

S005 · calculation

Before

Expectation ORIGINAL weight total through slot3 := sum(20, 0)

After

Expectation ORIGINAL weight total through slot3 = 20

Conditions: none

Use ORIGINAL operands and declared order for exact integer/rational arithmetic,not floats.Bounds are family-specific:do not revalidate derived values as RAW inputs or add blanket SAFE/n64 caps to BASE families.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S004

S006 · implies

Before

source roles = [[0, 1, 2, 3], powerset(S), [1, 13, 6, 0], 20, [-17, -17, -4, 1010], [-33, -33, -7, 2021]]

After

derived = [[0, 1, 2, 3], 20, Yes]

Conditions: none

S is nonempty,distinct and≤100;weights,X/Y align to ORIGINAL S slots.F is exactly powerset(S),weights nonnegative,denominator positive,and total EXACTLYden.EVEN at a=0 or null weights validate ALL raw fields;never silently uniformize.

Step identifiers and dependencies

Rule: Expectation_FULL_model_RAW_slots_SAME_alignment_and_normalized_law · Uses: G001, S005

S007 · calculation

Before

Expectation SAME outcome slot0 ORIGINAL X plus Y := sum(-17, -33)

After

Expectation SAME outcome slot0 ORIGINAL X plus Y = -50

Conditions: none

Use ORIGINAL operands and declared order for exact integer/rational arithmetic,not floats.Bounds are family-specific:do not revalidate derived values as RAW inputs or add blanket SAFE/n64 caps to BASE families.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S006

S008 · implies

Before

source roles = [0, 0, sum_expectation, -17, -33, not-supplied, not-supplied, not-supplied]

After

derived = [-50]

Conditions: none

Transform at EACH ORIGINAL outcome BEFORE using its aligned weight.Never sort S,X,Y,weights independently.Null-weight values remain original data;do not delete them to repair inputs or infer a range.

Step identifiers and dependencies

Rule: Expectation_EACH_original_outcome_transformation_BEFORE_weight · Uses: G001, S007

S009 · calculation

Before

Expectation ORIGINAL slot0 weight times transformed value := mul(1, -50)

After

Expectation ORIGINAL slot0 weight times transformed value = -50

Conditions: none

Use ORIGINAL operands and declared order for exact integer/rational arithmetic,not floats.Bounds are family-specific:do not revalidate derived values as RAW inputs or add blanket SAFE/n64 caps to BASE families.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S008

S010 · calculation

Before

Expectation ORIGINAL weighted numerator through slot0 := sum(0, -50)

After

Expectation ORIGINAL weighted numerator through slot0 = -50

Conditions: none

Use ORIGINAL operands and declared order for exact integer/rational arithmetic,not floats.Bounds are family-specific:do not revalidate derived values as RAW inputs or add blanket SAFE/n64 caps to BASE families.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S009

S011 · calculation

Before

Expectation SAME outcome slot1 ORIGINAL X plus Y := sum(-17, -33)

After

Expectation SAME outcome slot1 ORIGINAL X plus Y = -50

Conditions: none

Use ORIGINAL operands and declared order for exact integer/rational arithmetic,not floats.Bounds are family-specific:do not revalidate derived values as RAW inputs or add blanket SAFE/n64 caps to BASE families.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S010

S012 · implies

Before

source roles = [1, 1, sum_expectation, -17, -33, not-supplied, not-supplied, not-supplied]

After

derived = [-50]

Conditions: none

Transform at EACH ORIGINAL outcome BEFORE using its aligned weight.Never sort S,X,Y,weights independently.Null-weight values remain original data;do not delete them to repair inputs or infer a range.

Step identifiers and dependencies

Rule: Expectation_EACH_original_outcome_transformation_BEFORE_weight · Uses: G001, S011

S013 · calculation

Before

Expectation ORIGINAL slot1 weight times transformed value := mul(13, -50)

After

Expectation ORIGINAL slot1 weight times transformed value = -650

Conditions: none

Use ORIGINAL operands and declared order for exact integer/rational arithmetic,not floats.Bounds are family-specific:do not revalidate derived values as RAW inputs or add blanket SAFE/n64 caps to BASE families.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S012

S014 · calculation

Before

Expectation ORIGINAL weighted numerator through slot1 := sum(-50, -650)

After

Expectation ORIGINAL weighted numerator through slot1 = -700

Conditions: none

Use ORIGINAL operands and declared order for exact integer/rational arithmetic,not floats.Bounds are family-specific:do not revalidate derived values as RAW inputs or add blanket SAFE/n64 caps to BASE families.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S013

S015 · calculation

Before

Expectation SAME outcome slot2 ORIGINAL X plus Y := sum(-4, -7)

After

Expectation SAME outcome slot2 ORIGINAL X plus Y = -11

Conditions: none

Use ORIGINAL operands and declared order for exact integer/rational arithmetic,not floats.Bounds are family-specific:do not revalidate derived values as RAW inputs or add blanket SAFE/n64 caps to BASE families.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S014

S016 · implies

Before

source roles = [2, 2, sum_expectation, -4, -7, not-supplied, not-supplied, not-supplied]

After

derived = [-11]

Conditions: none

Transform at EACH ORIGINAL outcome BEFORE using its aligned weight.Never sort S,X,Y,weights independently.Null-weight values remain original data;do not delete them to repair inputs or infer a range.

Step identifiers and dependencies

Rule: Expectation_EACH_original_outcome_transformation_BEFORE_weight · Uses: G001, S015

S017 · calculation

Before

Expectation ORIGINAL slot2 weight times transformed value := mul(6, -11)

After

Expectation ORIGINAL slot2 weight times transformed value = -66

Conditions: none

Use ORIGINAL operands and declared order for exact integer/rational arithmetic,not floats.Bounds are family-specific:do not revalidate derived values as RAW inputs or add blanket SAFE/n64 caps to BASE families.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S016

S018 · calculation

Before

Expectation ORIGINAL weighted numerator through slot2 := sum(-700, -66)

After

Expectation ORIGINAL weighted numerator through slot2 = -766

Conditions: none

Use ORIGINAL operands and declared order for exact integer/rational arithmetic,not floats.Bounds are family-specific:do not revalidate derived values as RAW inputs or add blanket SAFE/n64 caps to BASE families.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S017

S019 · calculation

Before

Expectation SAME outcome slot3 ORIGINAL X plus Y := sum(1010, 2021)

After

Expectation SAME outcome slot3 ORIGINAL X plus Y = 3031

Conditions: none

Use ORIGINAL operands and declared order for exact integer/rational arithmetic,not floats.Bounds are family-specific:do not revalidate derived values as RAW inputs or add blanket SAFE/n64 caps to BASE families.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S018

S020 · implies

Before

source roles = [3, 3, sum_expectation, 1010, 2021, not-supplied, not-supplied, not-supplied]

After

derived = [3031]

Conditions: none

Transform at EACH ORIGINAL outcome BEFORE using its aligned weight.Never sort S,X,Y,weights independently.Null-weight values remain original data;do not delete them to repair inputs or infer a range.

Step identifiers and dependencies

Rule: Expectation_EACH_original_outcome_transformation_BEFORE_weight · Uses: G001, S019

S021 · calculation

Before

Expectation ORIGINAL slot3 weight times transformed value := mul(0, 3031)

After

Expectation ORIGINAL slot3 weight times transformed value = 0

Conditions: none

Use ORIGINAL operands and declared order for exact integer/rational arithmetic,not floats.Bounds are family-specific:do not revalidate derived values as RAW inputs or add blanket SAFE/n64 caps to BASE families.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S020

S022 · calculation

Before

Expectation ORIGINAL weighted numerator through slot3 := sum(-766, 0)

After

Expectation ORIGINAL weighted numerator through slot3 = -766

Conditions: none

Use ORIGINAL operands and declared order for exact integer/rational arithmetic,not floats.Bounds are family-specific:do not revalidate derived values as RAW inputs or add blanket SAFE/n64 caps to BASE families.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S021

S023 · calculation

Before

Expectation ORIGINAL weighted numerator over denominator := div(-766, 20)

After

Expectation ORIGINAL weighted numerator over denominator = -383/10

Conditions: none

Use ORIGINAL operands and declared order for exact integer/rational arithmetic,not floats.Bounds are family-specific:do not revalidate derived values as RAW inputs or add blanket SAFE/n64 caps to BASE families.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S022

S024 · implies

Before

source roles = [[0, 1, 2, 3], [1, 13, 6, 0], 20, sum_expectation, [-50, -50, -11, 3031]]

After

derived = [[-50, -650, -66, 0], -766, -383/10]

Conditions: none

In the QUALIFIED SAME probability law,E[Z]=Σw_iZ(s_i)/q.Affine gives aE[X]+b and a same-model sum gives E[X]+E[Y]WITHOUT independence;this does not imply a product-expectation formula.A constant has mean c because total mass is1.Negative/unattained means are legal;retain/1.

Step identifiers and dependencies

Rule: Expectation_LINEARITY_qualified_SAME_law_NOT_independence_or_sample_mean · Uses: G001, S023

Reverse checks

  • S024 · premise_and_result_audit — Reverse-check the ORIGINAL inputs,field roles,domain and premises.Consistency does not imply unique recovery of premises.Keep finite checking,independent review,formal proof and publication separate.
  • S023 · premise_and_result_audit — Recompute Expectation ORIGINAL weighted numerator over denominator with exact rational arithmetic, not rounded decimals.
  • S022 · premise_and_result_audit — Recompute Expectation ORIGINAL weighted numerator through slot3 with exact rational arithmetic, not rounded decimals.
  • S021 · premise_and_result_audit — Recompute Expectation ORIGINAL slot3 weight times transformed value with exact rational arithmetic, not rounded decimals.
  • S020 · premise_and_result_audit — Reverse-check the ORIGINAL inputs,field roles,domain and premises.Consistency does not imply unique recovery of premises.Keep finite checking,independent review,formal proof and publication separate.
  • S019 · premise_and_result_audit — Recompute Expectation SAME outcome slot3 ORIGINAL X plus Y with exact rational arithmetic, not rounded decimals.
  • S018 · premise_and_result_audit — Recompute Expectation ORIGINAL weighted numerator through slot2 with exact rational arithmetic, not rounded decimals.
  • S017 · premise_and_result_audit — Recompute Expectation ORIGINAL slot2 weight times transformed value with exact rational arithmetic, not rounded decimals.
  • S016 · premise_and_result_audit — Reverse-check the ORIGINAL inputs,field roles,domain and premises.Consistency does not imply unique recovery of premises.Keep finite checking,independent review,formal proof and publication separate.
  • S015 · premise_and_result_audit — Recompute Expectation SAME outcome slot2 ORIGINAL X plus Y with exact rational arithmetic, not rounded decimals.
  • S014 · premise_and_result_audit — Recompute Expectation ORIGINAL weighted numerator through slot1 with exact rational arithmetic, not rounded decimals.
  • S013 · premise_and_result_audit — Recompute Expectation ORIGINAL slot1 weight times transformed value with exact rational arithmetic, not rounded decimals.
  • S012 · premise_and_result_audit — Reverse-check the ORIGINAL inputs,field roles,domain and premises.Consistency does not imply unique recovery of premises.Keep finite checking,independent review,formal proof and publication separate.
  • S011 · premise_and_result_audit — Recompute Expectation SAME outcome slot1 ORIGINAL X plus Y with exact rational arithmetic, not rounded decimals.
  • S010 · premise_and_result_audit — Recompute Expectation ORIGINAL weighted numerator through slot0 with exact rational arithmetic, not rounded decimals.
  • S009 · premise_and_result_audit — Recompute Expectation ORIGINAL slot0 weight times transformed value with exact rational arithmetic, not rounded decimals.
  • S008 · premise_and_result_audit — Reverse-check the ORIGINAL inputs,field roles,domain and premises.Consistency does not imply unique recovery of premises.Keep finite checking,independent review,formal proof and publication separate.
  • S007 · premise_and_result_audit — Recompute Expectation SAME outcome slot0 ORIGINAL X plus Y with exact rational arithmetic, not rounded decimals.
  • S006 · premise_and_result_audit — Reverse-check the ORIGINAL inputs,field roles,domain and premises.Consistency does not imply unique recovery of premises.Keep finite checking,independent review,formal proof and publication separate.
  • S005 · premise_and_result_audit — Recompute Expectation ORIGINAL weight total through slot3 with exact rational arithmetic, not rounded decimals.
  • S004 · premise_and_result_audit — Recompute Expectation ORIGINAL weight total through slot2 with exact rational arithmetic, not rounded decimals.
  • S003 · premise_and_result_audit — Recompute Expectation ORIGINAL weight total through slot1 with exact rational arithmetic, not rounded decimals.
  • S002 · premise_and_result_audit — Recompute Expectation ORIGINAL weight total through slot0 with exact rational arithmetic, not rounded decimals.
  • S001 · premise_and_result_audit — Reverse-check the ORIGINAL inputs,field roles,domain and premises.Consistency does not imply unique recovery of premises.Keep finite checking,independent review,formal proof and publication separate.

Result

-383/10

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: 75298b1af335251c637073b1ad238129559664d2ca75bdce08817d498d6a48b6
  • candidate record SHA-256: a4ebe6b975c5f69ad5f659cc1cc1d670c78d10cb6421ca597e18d6569504d81b
  • semantic review receipt SHA-256: 963099ffc9f754069fdce6792949a85ed350472465eaceb3038fa8011cf672bd
  • question-first witness SHA-256: d7655324c5d11528e1af90b757384cebd3313e19dc5f6f5b9b8ea7624fb06f6f
  • Lean: NOT_RUN · human review: NOT_PERFORMED
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