How do you estimate effort and timelines for a project?
What the interviewer wants to hear
- Break work into small pieces using a WBS
- Involve the people who will do the work
- Use techniques: analogous, three-point, story points
- Include risk buffers and dependencies
- Refine estimates as you learn
Model answer
I start by breaking the work into small, clear pieces using a work breakdown structure, because small tasks are easier to estimate. I always involve the people who will do the work, since their estimates are more accurate and they feel ownership. I use historical data from similar projects where possible, which is analogous estimating. For uncertain tasks I use three-point estimates with optimistic, most likely and pessimistic values. In agile teams we use story points and the team velocity to forecast. Then I map dependencies and the critical path, and add contingency for known risks rather than padding every task. I share estimates as ranges with assumptions, not single fixed numbers, and I refine them as we learn more during the project.
Can you answer it under time pressure?
Take a timed medium round and get scored on every answer.
More medium Project Manager questions
- How do you prevent and handle scope creep?
- How would you handle a team member who is underperforming?
- How do you deliver bad news, like a delay, to your sponsor?
- How do you manage dependencies on other teams that you do not control?
- Explain earned value management and how you use it on a project.
- Walk me through how you run change control on a project.
- How do you decide which contract type to use with a vendor?
- How do you plan and run a project kickoff meeting?
- How do you build and control a project budget?