Effort-time estimation

Basic idea

Estimate the effort (work) and time (duration) for each task. The two are not interchangeable — Brooks’s mythical man-month: adding people to a late project makes it later.

Key formulas

• PERT three-point: $T_E = (O + 4M + P)/6$
• PERT std dev: $\sigma = (P - O)/6$
• COCOMO schedule from effort: $T_{dev} = 2.5 \cdot E^{0.38}$ months (organic)

Effort-time estimation

A common measure for estimating the effort for software is man-months

The mythical man-month

• man-months is a misleading measure to estimate software.
• adding people to a project that is behind schedule could result in more damage than helping it.

Time Estimation

• optimistic time O
• pessimistic time P
• most likely time M
• expected time TE

TE = ( O + 4*M + P)/6

Siblings

• Definitions
• Developing Project Schedule
• Earned Value Analysis (EVA)
• Milestones vs Deliverables
• PERT (Program Evaluation and Review Technique) chart
• Planning in Agile
• Project Schedule
• Project Scheduling
• Project Tracking and Control
• Tasks