Understanding PERT AnalysisLearn project estimation with three-point analysis
What is PERT?
PERT (Program Evaluation and Review Technique) is a project management method for planning and controlling complex projects. It uses three time estimates (optimistic, most likely, pessimistic) to calculate expected task duration and identify critical paths.
Why It Matters
PERT matters because: 1) Handles uncertainty - uses three estimates instead of one, 2) Identifies critical path - shows which tasks delay the project, 3) Improves accuracy - statistical approach reduces estimation errors, 4) Shows flexibility - reveals where slack exists, 5) Risk awareness - pessimistic estimates highlight potential delays.
Expected Duration
29.3 days
Std Deviation
±2.5
Critical Tasks
1
Total Tasks
5
Task Duration Estimates
Completion Confidence
PERT Task Analysis
| Task | Optimistic | Most Likely | Pessimistic | PERT Expected | Std Dev | Start | Finish | |
|---|---|---|---|---|---|---|---|---|
| 3.2 | 3.0 | 0.0 | 3.2 | |||||
| 6.3 | 6.0 | 3.2 | 9.5 | |||||
| 12.7 | 12.0 | 9.5 | 22.2 | |||||
| 5.2 | 5.0 | 19.0 | 24.2 | |||||
| 2.0 | 2.0 | 17.8 | 19.8 | |||||
| Project Total | 29.3 | ±2.5 |
PERT Formula Reference
Expected Duration
E = (O + 4M + P) / 6
Weights most likely 4x more than optimistic/pessimistic
Standard Deviation
σ = (P - O) / 6
Higher = more uncertainty in estimate
Project Variance
σ² = Σ((P-O)/6)²
Sum of all task variances
PERT Calculator Glossary
PERT
Program Evaluation and Review Technique - a project management method using three time estimates for better planning.
Three-Point Estimate
Estimation method using three values: optimistic, most likely, and pessimistic to calculate expected duration.
Optimistic Time (O)
Best-case scenario estimate - everything goes perfectly. Represents about 1% probability of occurrence.
Most Likely Time (M)
Realistic estimate considering normal challenges. The most probable outcome based on experience.
Pessimistic Time (P)
Worst-case scenario estimate - everything that can go wrong does. Represents about 1% probability.
Expected Time
Weighted average using formula (O + 4M + P) / 6. Provides statistically most likely duration.
Standard Deviation (σ)
Measure of uncertainty/variability in estimates. Higher σ means less certainty in predictions.
Critical Path
Longest sequence of dependent tasks determining minimum project duration. Delays here delay the project.
Slack/Float
Time a task can be delayed without delaying project completion. Zero slack = critical task.
Variance
Statistical measure of uncertainty squared. Used to calculate project-level standard deviation.