CompTIA Project+ (PK0-005)Project Life Cycle PhasesHard
A project manager is developing the initial project schedule and needs to estimate the duration of a complex, novel activity for which historical data is scarce. The team provides three estimates: an optimistic estimate of 10 days, a pessimistic estimate of 30 days, and a most likely estimate of 17 days. Which technique should the project manager use to determine the MOST realistic duration estimate for this activity?
- AParametric Estimating
- BBottom-Up Estimating
- CAnalogous Estimating
- DThree-Point Estimating (PERT)
Show answer & explanationAnswer & explanation
Correct answer: D. Three-Point Estimating (PERT)
Three-Point Estimating, particularly using the PERT (Program Evaluation and Review Technique) formula, is designed for situations with uncertainty and limited historical data. It uses optimistic (O), pessimistic (P), and most likely (M) estimates to calculate a weighted average (E = (O + 4M + P) / 6), providing a more realistic and statistically sound duration estimate.
Why the other options are wrong
- A. Parametric estimating uses statistical relationships between historical data and other variables, which is also limited here.
- B. Bottom-up estimating involves aggregating estimates from lower-level components and doesn't inherently handle the uncertainty of a novel activity with three distinct estimates in this manner.
- C. Analogous estimating uses historical data from similar projects, which is scarce in this scenario.
Three-Point Estimating (PERT)
An estimating technique that uses three estimates (optimistic, pessimistic, and most likely) to define an approximate range for an activity's duration or cost.
- PERT formula: (Optimistic + 4 * Most Likely + Pessimistic) / 6.
- Accounts for uncertainty and risk.
- Provides a weighted average, more reliable than a single point estimate.
Memory trick: When facing 'fuzzy' duration, use 'three' points to 'sharpen' your estimate.