Badr Alghamdi
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The opening date

Follow one promise through approval, uncertainty, float and the last delivery.

This is a fictional case. The axis counts elapsed days from 1 January 2026, and the operation works every civil day. The simulations use fixed seeds, so the same inputs always give the same sample. Nothing here settles an entitlement, a compensation amount or the ownership of float.

1. The first promise

A duration is proposed for this project. Beside it sits a fictional record of 10 earlier projects and the days each one took. Nothing in the case proves those projects are comparable to this one. Assume comparability for this arithmetic and read the answer under that limit. A project that finished exactly on the proposed day counts as meeting it.

Available facts
  • Day 0 on the axis
  • Calendar basisEvery civil day operates
  • Reference projects10 projects

Inputs and givens

days

Case range: 150 to 600 days.

What share of this reference class finished by the proposed day?

Percent of the reference class. Within 1 percentage point.

Within 1 percentage point From 0 to 100.

The score is a target for this attempt. It is not a judgement of you.

Typing the model's own answer earns full marks.

A number within the stated tolerance earns 10 points. Beyond it, each further tolerance removes 1 point, down to 0.

Reference project
The promise against the reference classThe reference durations and the proposed day sit on one axis. No share is shown before the check.200400600800Days from the startOriginal promise300

Numbers appear after the check.

Each mark is one fictional reference project, on the same day axis as the promise.
The 10 fictional reference durations, in the order the case gives them.
ProjectDays
Reference project 1255
Reference project 2285
Reference project 3320
Reference project 4340
Reference project 5360
Reference project 6390
Reference project 7425
Reference project 8470
Reference project 9540
Reference project 10630

How this check is calculated

b+eN=pc\frac{b+e}{N}=p_c

The share counts the reference durations at or below the promise and divides by the number of projects. A duration equal to the promise counts as meeting it.

Show the full maths

Symbols and assumptions

b+eN=pcb=∑j=1N1(xj<P),e=∑j=1N1(xj=P)q.8=x(⌈.8N⌉)\begin{gathered}\frac{b+e}{N}=p_c\\b=\sum_{j=1}^{N}\mathbf{1}(x_j<P),\qquad e=\sum_{j=1}^{N}\mathbf{1}(x_j=P)\\q_{.8}=x_{(\lceil .8N\rceil)}\end{gathered}

b counts the durations below the promise and e counts the durations equal to it. N is the number of reference projects. The class P80 takes the nearest rank in the sorted durations, so it is always one of the observed durations. The class describes other projects. It adds no days to this plan.

Every duration, rate, budget and date in this case is fictional. The books explain the mechanisms and supply none of these numbers.

The outside view

Check this step before continuing.

Sources

Three books supply context for the mechanisms. Every duration, rate, budget and date in this case is fictional.

  • Bent Flyvbjerg and Dan Gardner, How Big Things Get Done: The Surprising Factors That Determine the Fate of Every Project, from Home Renovations to Space Exploration and Everything in Between, Currency, 2023.

    Reference classes and the view from outside one plan

  • Eliyahu M. Goldratt, Critical Chain, North River Press, 1997.

    Local allowances inside a quoted duration

  • Sam L. Savage, The Flaw of Averages: Why We Underestimate Risk in the Face of Uncertainty, John Wiley and Sons, 2009.

    Averages, distributions and the cost of a late date

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The opening date

Follow one promise through approval, uncertainty, float and the last delivery.

This is a fictional case. The axis counts elapsed days from 1 January 2026, and the operation works every civil day. The simulations use fixed seeds, so the same inputs always give the same sample. Nothing here settles an entitlement, a compensation amount or the ownership of float.

Journey incomplete

1. The first promise

A duration is proposed for this project. Beside it sits a fictional record of 10 earlier projects and the days each one took. Nothing in the case proves those projects are comparable to this one. Assume comparability for this arithmetic and read the answer under that limit. A project that finished exactly on the proposed day counts as meeting it.

  • Day 0 on the axis
  • Calendar basisEvery civil day operates
  • Reference projects10 projects

Not checked in this attempt

  • Proposed duration300

How this check is calculated

b+eN=pc\frac{b+e}{N}=p_c

The share counts the reference durations at or below the promise and divides by the number of projects. A duration equal to the promise counts as meeting it.

Show the full maths

Symbols and assumptions

b+eN=pcb=∑j=1N1(xj<P),e=∑j=1N1(xj=P)q.8=x(⌈.8N⌉)\begin{gathered}\frac{b+e}{N}=p_c\\b=\sum_{j=1}^{N}\mathbf{1}(x_j<P),\qquad e=\sum_{j=1}^{N}\mathbf{1}(x_j=P)\\q_{.8}=x_{(\lceil .8N\rceil)}\end{gathered}

b counts the durations below the promise and e counts the durations equal to it. N is the number of reference projects. The class P80 takes the nearest rank in the sorted durations, so it is always one of the observed durations. The class describes other projects. It adds no days to this plan.

Every duration, rate, budget and date in this case is fictional. The books explain the mechanisms and supply none of these numbers.

The outside view

2. The approval chain

Not reached in this attempt

3. What the task estimates mean

Not reached in this attempt

4. The float already spent

Not reached in this attempt

5. The last delivery and the ready site

Not reached in this attempt

6. The opening account

Not reached in this attempt

Your opening date record

Journey incomplete

    Only checked steps appear in this account. Unchecked steps and their later results are left out.

    0 from 0 checked steps

    Final possible total: 60 points

    Checks in this attempt

    The score is a target for this attempt. It is not a judgement of you. Typing the model's own answer earns full marks.

    A number within the stated tolerance earns 10 points. Beyond it, each further tolerance removes 1 point, down to 0.

    Sources

    Three books supply context for the mechanisms. Every duration, rate, budget and date in this case is fictional.

    • Bent Flyvbjerg and Dan Gardner, How Big Things Get Done: The Surprising Factors That Determine the Fate of Every Project, from Home Renovations to Space Exploration and Everything in Between, Currency, 2023.

      Reference classes and the view from outside one plan

    • Eliyahu M. Goldratt, Critical Chain, North River Press, 1997.

      Local allowances inside a quoted duration

    • Sam L. Savage, The Flaw of Averages: Why We Underestimate Risk in the Face of Uncertainty, John Wiley and Sons, 2009.

      Averages, distributions and the cost of a late date