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Equation 4 · Evaluating Trajectories, Not Answers

What does this equation mean?

E[cost to first success]=cˉp,\mathbb{E}[\text{cost to first success}] = \frac{\bar{c}}{p},

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Start withbarc
Divide byp
This relates toE[cost to first success]
How to read the two sides of this formula. Follow the article passage for the meaning of each quantity.

This equation states an equality: the expressions on both sides have the same value under the article’s assumptions. Read the equation part by part below; each part has a contextual explanation and a link to its mathematical background.

Read it piece by piece

E\mathbb{E}

Symbol E

The expected value operator: the probability-weighted average of the quantity inside its brackets.

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cˉ\bar{c}

Symbol barc

barc occurs above the fraction bar. The numerator is divided by the entire denominator below it.

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pp

Symbol p

the probability.

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=

=

The expressions on both sides represent the same quantity under the stated assumptions.

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fraction

fraction

Divide the expression above the line by the one below it.

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How to interpret it

With a fixed numerator, increasing a nonzero denominator reduces the fraction. Read it with the definitions, units, and assumptions supplied by the article.

What the article says around this equation

There is also a structural reason cost cannot be separated from reliability. If a run costs cˉ\bar{c} on average and succeeds with probability p , and the operator simply retries until success, the expected spend to first success is E[cost to first success]=cˉp\mathbb{E}[\text{cost to first success}] = \frac{\bar{c}}{p}. which means a cheap unreliable agent and an expensive reliable one can occupy the same operating point. Reporting either number alone conceals which one you have bought. The honest artefact is a curve — quality against spend, produced by sweeping the effort level and the retry policy — rather than a point, and the honest comparison places two systems at matched spend and asks which reaches further.

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Sources cited in the article section

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