PERT — three-point estimates

For tasks where the duration is uncertain, capture a three-point estimate and let the scheduling engine use the expected value in CPM math.

**Turning it on**
On the Tasks tab, click the **PERT** toggle button. Three small columns (O / L / P) appear inline next to the dates column.

**The three numbers (in days)**
• **O** — Optimistic. Best case if everything goes right
• **L** — Likely. Your expected duration with normal hiccups
• **P** — Pessimistic. Worst case short of the project being cancelled

**The math**
• Expected duration = (O + 4·L + P) / 6 — beta-distribution mean
• σ (standard deviation) = (P − O) / 6 — risk indicator

When all three are filled, the Critical Path engine uses the expected duration instead of the authored end-minus-start. The Tasks tab shows "Expected X.Xd · σ ±X.Xd" beneath the date range.

**When to use it**
• Estimates that span weeks/months where the spread matters
• Tasks with high uncertainty (research, regulatory approval, weather-dependent work)
• When you want stakeholders to understand the risk, not just the median

**When not to use it**
• Tasks with hard deadlines (regulatory date, meeting day) — fixed dates beat probabilistic estimates
• Tasks under a week — the spread is usually too small to matter

Wally can set estimates: "Set a PERT estimate on the foundation pour: 5 days optimistic, 7 likely, 14 pessimistic" — confirm-first action card.