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Drill65 minutesUnit 6 of 8 · Lesson 2 of 3

Numbers without a data team

MayaWed 09:50

Maya reads your finding and asks one question: how many people does this actually hit? The data team can tell you. Next quarter.

Estimate out loud, so people argue with the guess

  1. Next quarter

    01 Next quarter

    The question is simple. The answer is stuck behind a queue you do not control.

  2. Numbers you can guess

    02 Numbers you can guess

    Signups a month, the share who link a bank, the share who hit the problem, what each one is worth. Four guesses, multiplied.

  3. A range, not a point

    03 A range, not a point

    Give a low, a middle and a high. One confident number gets blind agreement or blind refusal.

  4. Find the guess it swings on

    04 Find the guess it swings on

    Move each guess in turn. The one that moves the answer most is the one to go and check.

How Enrico Fermi handled it

EN

Enrico Fermi

1945

Public commentary. No affiliation.
The situation

At the first atomic test, Fermi wanted a rough idea of the blast's strength long before the instruments could be read.

What they did

He dropped scraps of paper as the shock wave passed, paced out how far they moved, and estimated about ten kilotons. The measured figure, which came much later, was around twenty. Off by half, right about the size of the thing, from paper and a few seconds.

Why it matters to you

An estimate with its workings showing is useful long before the precise number exists. Roughly right this week beats exactly right next quarter.

Doing it with AI, and where it breaks

The move

Have a model lay the estimate out as a chain, then check its arithmetic and, more importantly, every number it assumed.

The trap

Its guesses come from the average of the internet: US prices, US conversion rates, US salaries. Give it Sona's numbers, or make it mark every one it made up.

Prompt worth stealing

I need to estimate [the number, with a unit and a time period]. Break it into no more than five multiplied factors. For each, give a low and a high guess and say exactly where the guess comes from. Mark any factor you made up. Then tell me which factor the result is most sensitive to.

Build it

The artefact

A sized opportunity: five guesses or fewer, each with a reason, and a low, middle and high.

Google Sheets

0/5

The worked solution

Stuck, or want to compare?

There is a worked solution. Try the build first. Reading it before you have attempted anything is the fastest way to learn nothing.

Checkpoint

If you did the build, these take two minutes. If you cannot answer one of them, that is the part to go back to.

Moving on marks this lesson complete. Finish the build first, it is the part that counts.

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