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Question 28955: Exact Median of an Odd or Even Observation List

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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R0056-28955 · q-20261005-advance-20261006-r07-descriptive-statistics-0030

Original question and givens

The nonempty observation list is D=[-7, -7, 2, 8, 8]. Retain every repetition. Find the median after sorting: one middle value for odd length, or the average of the two middle values for even length. Give a reduced fraction with positive denominator, retaining /1 for integers.

  • G001 — The nonempty observation list is D=[-7, -7, 2, 8, 8]. Retain every repetition. Find the median after sorting: one middle value for odd length, or the average of the two middle values for even length. Give a reduced fraction with positive denominator, retaining /1 for integers.

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-statistics-observation-median, observation_median]

After

derived = [odd_middle_or_even_two_middle_mean]

Conditions: none

Use the declared scalar/set/Yes-No/fraction answer role;integer fractions retain/1.Do not add an undeclared domain or change original bilingual data,formulas or questions.

Step identifiers and dependencies

Rule: R56_source_answer_role_and_EXACT_family_interface · Uses: G001

S002 · implies

Before

source roles = [[-7, -7, 2, 8, 8]]

After

derived = [[-7, -7, 2, 8, 8], 5]

Conditions: none

Retain EVERY observation,including repeated values.Numeric sorting changes order only,not n or the sum;do not deduplicate as a set or sort lexically.These are sample summaries,not inferred population laws.

Step identifiers and dependencies

Rule: Statistics_FULL_observations_MULTIPLICITY_and_numeric_order · Uses: G001, S001

S003 · implies

Before

source roles = [[-7, -7, 2, 8, 8], 5]

After

derived = [2, 2]

Conditions: none

For odd n use sorted zero-based index n//2,with(n-1)/2 entries on each side,not the original unsorted index.

Step identifiers and dependencies

Rule: Statistics_ODD_median_actual_middle_order_statistic · Uses: G001, S002

Reverse checks

  • S003 · premise_and_result_audit — Reverse-check EACH original datum and premise,retaining indices,signs and strict/non-strict boundaries.A correct final answer cannot replace the derivation obligations.This is candidate teaching/exact checking,not formal proof or publication clearance.
  • S002 · premise_and_result_audit — Reverse-check EACH original datum and premise,retaining indices,signs and strict/non-strict boundaries.A correct final answer cannot replace the derivation obligations.This is candidate teaching/exact checking,not formal proof or publication clearance.
  • S001 · premise_and_result_audit — Reverse-check EACH original datum and premise,retaining indices,signs and strict/non-strict boundaries.A correct final answer cannot replace the derivation obligations.This is candidate teaching/exact checking,not formal proof or publication clearance.

Result

2/1

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: 5e3d4de7bb55591e717fc7f7e60b64c24b201bb5fae8f3f622d0605e59cccffa
  • candidate record SHA-256: 12a37e752653cd7014e21798a76bdf623a59d4696e0b79118790080096131ef6
  • semantic review receipt SHA-256: 8bbda4edbed7078634ae88342998c79bcfb95de96187fac119c3b08e0adb0bc8
  • question-first witness SHA-256: 3edafa72d63d16a22414892b55806430e0a25b15b926d04f312550179607759f
  • Lean: NOT_RUN · human review: NOT_PERFORMED
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