vault backup: 2026-04-02 22:27:54
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@@ -2,7 +2,12 @@
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id:
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aliases: []
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title: ConEst Senior Review
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tags: []
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tags:
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- authorship/original
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- destiny/permanent
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- occupational
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- status/not-started
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- type/process
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dg-publish: true
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---
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# ConEst Senior Review
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@@ -188,7 +188,7 @@ As of when?
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> How many gallons are in a bushel (they are both measures of volume)?
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I wonder if Hubbard had the same thought I did
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while reading [[macgregor_1994_judgemental-decomposition|MacGregor et al. (1994)]].
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while reading [[macgregor_1994_judgmental-decomposition|MacGregor et al. (1994)]].
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> How many sovereign rulers has England had in the last thousand years?
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+10
-4
@@ -16,8 +16,14 @@ especially if they sincerely believe
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that their success _was_ due to their competence.
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%%
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Books concerned with lucky fools:
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[[taleb_2001_fooled-by-randomness]]
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[[kahneman_2011_thinking]]
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[[hubbard_2020_failure]]
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somewhat related:
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* [hot hand fallacy](https://en.wikipedia.org/wiki/Hot_hand)
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* [gambler's fallacy](https://en.wikipedia.org/wiki/Gambler%27s_fallacy)
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%%
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%%
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Books concerned with lucky fools:
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* [[taleb_2001_fooled-by-randomness]]
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* [[kahneman_2011_thinking]]
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* [[hubbard_2020_failure]]
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%%
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+6
-1
@@ -2,7 +2,12 @@
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id:
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aliases: []
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title: Megan Blizard
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tags: []
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tags:
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- authorship/original
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- destiny/permanent
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- occupational
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- status/not-started
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- type/person
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dg-publish: false
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---
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# Megan Blizard
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@@ -18,7 +18,7 @@ In [[hubbard_2020_failure#Break It Down, Then Do the Math]]
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Hubbard introduces **decomposition** as a method for reducing error in estimates,
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Providing Fermi's "piano tuners in Chicago" problem as an example,
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without acknowledging that _Fermi_ supplied the decomposition.
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Hubbard also references [[macgregor_1994_judgemental-decomposition]]
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Hubbard also references [[macgregor_1994_judgmental-decomposition]]
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which is a similar case.
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Neither of these examples suggest that decomposition is a magic bullet,
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_or even that a layman's decomposition wouldn't be worse than nothing._
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@@ -8,7 +8,9 @@ dg-publish: true
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---
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# 2026-01-25 22:59:??
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[[macgregor_1994_judgemental-decomposition]]
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## _Judgmental Decomposition_
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[[macgregor_1994_judgmental-decomposition]]
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I really hate this study.
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@@ -0,0 +1,42 @@
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---
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id: 2026-04-02T19:10:14-04:00
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aliases: []
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title: 2026-04-02 19:10:14
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tags:
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- authorship/original
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- destiny/permanent
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- status/draft
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- type/periodic/timestamped
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dg-publish: true
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date-created: 2026-04-02T19:10:14-04:00
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daily: "[[2026-04-02]]"
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weekly: "[[2026-W14]]"
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monthly: "[[2026-04]]"
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quarterly: "[[2026-Q2]]"
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yearly: "[[2026]]"
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---
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# 2026-04-02 19:10:14
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From a high-level, business proposition perspective
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[[construction-estimating]] is identical in function to stock trading,
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both typified by expert judgement under uncertainty
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...
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One significant difference despite their similarity
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is that only in stock trading is it well understood
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that individual loss is not only inevitable,
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_it is how the strategy works._
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If you're not losing sometimes
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you're not assuming enough risk
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and you're missing out on returns.
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Similar sentiments expressed in the context of construction contracting
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are not popular, and are frequently judged irresponsible.
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I believe the tendency to set standards for estimates
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beyond the optimal level of detail
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stems from a [cognitive bias of association](https://en.wikipedia.org/wiki/List_of_cognitive_biases#Association)
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or [relevance fallacy](https://en.wikipedia.org/wiki/List_of_fallacies#Relevance_fallacies)
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which leads otherwise rational estimators
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to the erroneous belief that because construction is physically tangible,
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risk control is more effective than in markets.
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This may be related to [[2026-04-02_20-41-59#Decomposition Fallacy]].
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@@ -0,0 +1,61 @@
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---
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id: 2026-04-02T20:41:59-04:00
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aliases: []
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title: 2026-04-02 20:41:59
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tags:
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- authorship/original
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- destiny/permanent
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- status/draft
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- type/periodic/timestamped
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dg-publish: true
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date-created: 2026-04-02T20:41:59-04:00
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daily: "[[2026-04-02]]"
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weekly: "[[2026-W14]]"
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monthly: "[[2026-04]]"
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quarterly: "[[2026-Q2]]"
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yearly: "[[2026]]"
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---
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# 2026-04-02 20:41:59
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## Decomposition Fallacy
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I have expressed in other notes[^1] my frustration
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with how estimate decomposition is most frequently explained:
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as an intuitive process which can not be performed incorrectly
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and by definition creates a more accurate estimate.
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[^1]: * [[2026-01-25_21-02-00]]
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* [[2026-01-25_22-59-00]]
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The argument that an estimate based on the aggregation of intermediate estimates
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is necessarily more reliable than one made in one go
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is intuitive, but a [non sequitur](https://en.wikipedia.org/wiki/Formal_fallacy).
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Frequently, decomposition is explicitly _unhelpful_
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due to its neglect of the [portfolio effect](https://financial-dictionary.thefreedictionary.com/portfolio+effect).
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If an estimator can give a high confidence estimate
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of total dollars spent on rental equipment over the life of a project,
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it does not follow that they could give one for
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dollars spent on scissor lifts alone with greater or even equal confidence.[^2]
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[^2]: I chose this example specifically
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because it has been an issue at both EC's I've estimated for.
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We set a target based on some well founded model
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(\$0.25 per direct labor hour or 1% of total sell price),
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then 3--4 decently paid estimators spend up to an hour
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discussing how to make that target
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from quantities and durations of individual pieces of equipment.
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Ultimately none are totally satisfied with it, nor should they be,
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since the actual quantities, durations, and equipment types will be quite different,
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and the entire exercise was pointless.
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My criticism is not entirely fair, however.
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Fermi and MacGregor's estimation problems have correct answers
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and are thus a different class entirely
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from those I'm most familiar with.
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I choose to criticize decomposition generally despite this
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because the distinction is rarely acknowledged by its advocates
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so "decomposition = good" pervades the estimating zeitgeist completely
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and I get baffled, horrified, or patronizing looks when I suggest
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that complete quantity takeoff may not be more accurate
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than a parametric budget that could be completed in a day.
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