estimate-calibrator

Replaces single-point guesses with structured three-point estimates: decomposes work into atomic units, estimates best/likely/worst case for each, identifies unknowns and assumptions, calculates aggregate ranges using PERT, and assigns confidence levels with explicit rationale.

| references/estimation-methods.md | PERT formula, three-point estimation, Monte Carlo basics | Always | | references/unknown-categories.md | Technical, scope, external, and organizational uncertainty types | Unknown identification | | references/calibration-tips.md | Cognitive biases in estimation, historical calibration, buffer strategies | Always |

| references/sizing-heuristics.md | Common task size patterns, complexity indicators, reference class data | Quick sizing needed |

Produces calibrated three-point estimates (best/likely/worst case) with explicit unknowns, confidence intervals, and assumption documentation. Breaks work into atomic units, identifies technical and scope uncertainties, calculates PERT ranges, and provides confidence rationale. Triggers on: "estimate this", "how long will this take", "effort estimate", "time estimate", "best case worst case", "confidence interval", "sizing", "estimate effort", "how big is this", "story points", "t-shirt sizing", "estimate the work", "PERT". NOT for task decomposition, implementation plans, or dependency mapping — use task-decomposer instead. Use this skill when a task or project needs an effort estimate with explicit uncertainty. Source: mathews-tom/praxis-skills.