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Equation 2 · Measuring AI Agent Architectures: Evidence, Benchmarks, and Uncertainty

What does this equation mean?

pat least one of k=1−(1−p)k,pall k succeed=pk.p_{\text{at least one of } k} = 1 - (1-p)^k, \qquad p_{\text{all } k \text{ succeed}} = p^k.

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Inputs and operations1 - (1-p)^k, qquad p_all k succeed = p^k
Result or conditionp_at least one of k
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.

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pat least one of kp_{\text{at least one of } k}

Symbol p_at least one of k

pap_at least one of k is part of the quantity the equation computes from the expression on the right.

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pp

Symbol p

the write.

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kk

Symbol k

k is part of the quantity the equation computes from the expression on the right.

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pall k succeedp_{\text{all } k \text{ succeed}}

Symbol p_all k succeed

pap_all k succeed is one of the signed contributions combined to compute the quantity on the left.

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pkp^k

Symbol p^k

pkp^k is one of the signed contributions combined to compute the quantity on the left.

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=

=

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

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subtraction

subtraction

Subtract the following term or group from the preceding one. A leading minus marks a negative quantity.

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subscript

subscript

The lower label selects a particular version, component, or indexed member of the quantity. For example, x₀ and xₜ can be values at different positions.

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superscript

superscript

A raised number can be a power. When it is a label or bound, it selects a case or the upper limit of a sum; the formula’s structure distinguishes these uses.

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How to interpret it

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What the article says around this equation

The distinction matters because the two metrics behave very differently even under the most favourable possible assumption — that trials are statistically independent. Write p for the probability that a single trial on a given task succeeds. Under independence, pat least one of k=1−(1−p)k,pall k succeed=pkp_{\text{at least one of } k} = 1 - (1-p)^k, \qquad p_{\text{all } k \text{ succeed}} = p^k. The first quantity rises quickly toward one as k grows, which is the intuitive but misleading sense in which “just try again” seems to fix unreliability. The second quantity falls quickly toward zero, and it is the quantity that matters if a task must be completed correctly on a specific occasion rather than merely being solvable in principle across several attempts.

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Sources cited in the article section

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