PERT Party — Weeks Estimator + Critical Path

Expected duration

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Units: weeks • TE = (O + 4M + P)/6

Uncertainty (SD)

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SD = (P − O)/6 • larger = more uncertainty

Confidence times

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Normal approx • uses TE and SD (see Help)

Activities

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Activity

Slack

Predecessors

Visual

Help & theory

PERT basics

Higher SD means more uncertainty. Use tags like scope, vendor, testing to connect estimates to PM knowledge areas.

Rollups & confidence

This app shows two common rollups:

Simple sum (all activities): TE_total = ΣTE, Var_total = ΣVar
Critical path rollup: only activities on the critical path contribute to project duration (based on TE). Variance is summed along the critical path (classic PERT assumption).

Confidence times assume a normal approximation: time ≈ TE + z·SD. This is a heuristic—use judgment for highly skewed work.

Critical path notes

Predecessors are IDs (comma‑separated). Example: A3 depends on A1, A2.
If there’s a cycle, missing predecessor ID, or other network issue, we’ll fall back to the simple sum rollup and explain the problem.

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