Project Management & Agile Module 4
Scheduling: networks, critical path and Gantt charts interview questions
Interview questions on “Scheduling: networks, critical path and Gantt charts”: warm-ups, then what each harder question tests and how a good answer starts.
Warm-up questions
Short questions with short answers, each answered in full.
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Fresher to mid
What are the four types of dependency in a schedule network?
Answered in the lesson Activities, dependencies and network diagrams
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Fresher to mid
What is the difference between total float and free float?
Total float is how long an activity can slip before the project's finish moves; free float is how long it can slip before any successor's early start moves. Free float is never larger than total float. An activity can have plenty of total float and no free float at all, when the next activity starts the moment it finishes: then any delay reaches that activity at once, although the finish has room. Total float tells the project manager which delays threaten the end date; free float tells the owners of the next activities whether a delay reaches them.
From the lesson The critical path method, step by step
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Fresher to mid
What is a schedule baseline, and why keep it once the plan has changed?
Answered in the lesson Gantt charts, calendars and schedule baselines
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Fresher to mid
What is the difference between crashing and fast-tracking?
Both shorten a schedule, and both work only on the critical path, but they spend different things. Crashing adds resources, people, equipment or overtime, to critical activities so that they take fewer days: it costs money, and the cheapest day is found from each activity's cost slope. Fast-tracking changes the logic instead, letting activities that were planned one after the other overlap: it costs little money but adds risk, because work that starts before its predecessor finishes may have to be redone.
From the lesson Resource levelling, crashing and fast-tracking
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Fresher to mid
What do P50 and P80 mean in a schedule risk analysis?
Answered in the lesson Three-point estimates and schedule risk analysis
Questions with model answers
What each question tests, the first step of a good answer and the follow-ups to expect.
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Mid to senior
You inherit a 300-activity schedule for a hospital wing in which 90 links carry lags, several of 20 days or more, and none has a note. The finish date looks fine. What do you do before you trust it?
- What it tests
- Knowing what lags hide, telling a genuine wait from hidden work or a hidden link, and fixing the logic rather than the dates.
- First step
- Export every lagged link with its predecessor, successor and lag, sort by size, and ask the owners what happens during each wait: nothing (curing, a notice period), someone's work, or a dependency on another activity.
- Follow-ups
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- How do you tell a lag that hides work from a genuine wait?
- What changes in the forecast once the hidden links are real?
- How do you stop the problem coming back?
From the lesson Activities, dependencies and network diagrams
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In the answer:
- Model answer
- Follow-up answers
- Common mistakes
- Rubric
- Variants
- about 2 minutes
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Fresher to mid
A product launch slipped by a week because the translated help pages were late, yet the schedule had shown the translation with 40 days of float. What most likely went wrong, and how would you have caught it?
- What it tests
- Recognising an open end or a missing successor, explaining why it produces false float, and naming the check that finds it.
- First step
- Look at the translation's successors in the schedule: if it has none, or only links that do not reach the launch milestone, its float was never real.
- Follow-ups
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- Why did the schedule show 40 days of float?
- Which checks would have found it before the launch?
- What else should you look for once you have found one open end?
From the lesson Activities, dependencies and network diagrams
Model answer, Pro.In the answer:
- Model answer
- Follow-up answers
- Common mistakes
- Rubric
- Variants
- about 2 minutes
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Mid to senior
A programme director asks you to mark every activity of a 120-activity schedule as critical, "so that nobody relaxes". How do you respond, and what do you offer instead?
- What it tests
- Knowing what critical means in CPM, what is lost when the word is diluted, and how to give management the focus it wants through float and near-critical paths.
- First step
- Agree with the aim, urgency, and show what the schedule loses: with everything "critical", nobody can tell which slips move the finish date. Then offer a view of the real critical path and the chains with little float.
- Follow-ups
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- What does marking everything critical do to the schedule's tools?
- How do you keep teams with float from relaxing?
- What would you report each week instead?
From the lesson The critical path method, step by step
Model answer, Pro.In the answer:
- Model answer
- Follow-up answers
- Common mistakes
- Rubric
- Variants
- about 2 minutes
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Mid to senior
After a contract milestone is entered as a "finish no later than" date, 40 activities in your schedule show negative float, from −3 to −15 days. Your sponsor asks whether the project is 15 days late. What do you tell them?
- What it tests
- Interpreting negative float, finding the path that really drives the milestone, and turning the numbers into options for a decision.
- First step
- Find the chain that drives the milestone, the one with −15, and check its logic and durations before reporting: negative float is only as real as the network it comes from.
- Follow-ups
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- Why do 40 activities show negative float if only one chain drives the milestone?
- What options would you put in front of the sponsor?
- Should you remove the constraint to make the float positive again?
From the lesson The critical path method, step by step
Model answer, Pro.In the answer:
- Model answer
- Follow-up answers
- Common mistakes
- Rubric
- Variants
- about 2 minutes
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Fresher to mid
A vendor's Gantt chart for your office fit-out shows every bar finishing a week before the move-in date, and the vendor says the project is on time. What would you ask to see before you believe it?
- What it tests
- Knowing that a Gantt chart is only a view, and asking for the logic, the calendar, the baseline and the status behind it.
- First step
- Ask for the schedule file or a report of its links, not the picture: are the bars linked to each other and to move-in, and were they recalculated from actual progress at a recent status date?
- Follow-ups
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- What could make a tidy chart wrong?
- Which calendar questions would you ask?
- What one report would you ask the vendor for each week?
From the lesson Gantt charts, calendars and schedule baselines
Model answer, Pro.In the answer:
- Model answer
- Follow-up answers
- Common mistakes
- Rubric
- Variants
- about 2 minutes
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Mid to senior
A sponsor asks you to bring a 60-day office relocation in 10 working days earlier, and offers a budget for it. How do you work out what to do, and what do you tell them?
- What it tests
- Using the critical path and cost slopes to crash in the right order, considering fast-tracking and its risk, watching for new critical paths, and presenting options with their cost and risk.
- First step
- List the critical activities and the near-critical chains with less than 10 days of float, and for each critical activity its shortest duration and its cost slope.
- Follow-ups
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- What changes once a second path becomes critical?
- When would you fast-track instead of crashing?
- What might make the 10 days impossible at any price?
From the lesson Resource levelling, crashing and fast-tracking
Model answer, Pro.In the answer:
- Model answer
- Follow-up answers
- Common mistakes
- Rubric
- Variants
- about 2 minutes
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Mid to senior
A software release is 3 weeks late with 5 weeks of work left, and a director wants to double the team of 6 next Monday. What do you advise?
- What it tests
- Applying Brooks's law with its reasons, separating work that splits from work that does not, and offering better levers than headcount alone.
- First step
- Look at the remaining work on the critical path and ask which parts can be split among new people without much teaching, and how many days the current team would spend bringing six people up to speed.
- Follow-ups
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- Is adding people ever the right answer late in a project?
- What would you do instead, or as well?
- How would you show the director the effect in numbers?
From the lesson Resource levelling, crashing and fast-tracking
Model answer, Pro.In the answer:
- Model answer
- Follow-up answers
- Common mistakes
- Rubric
- Variants
- about 2 minutes
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Mid to senior
A schedule risk analysis of a product launch gives P50 at working day 118 and P80 at day 131, while the plan's critical path says day 110. The sponsor wants one date for the press. What do you recommend, and how do you explain it?
- What it tests
- Turning a distribution into a commitment, sizing contingency from the analysis, explaining confidence in plain words, and keeping the date under control afterwards.
- First step
- Ask how costly a late announcement would be compared with an early one, because that sets the confidence the sponsor should choose; then show what each date means in those terms.
- Follow-ups
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- Why not announce day 110, the plan's date?
- How much contingency does your recommendation hold, and who controls it?
- What would make you change the date later?
From the lesson Three-point estimates and schedule risk analysis
Model answer, Pro.In the answer:
- Model answer
- Follow-up answers
- Common mistakes
- Rubric
- Variants
- about 2 minutes
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Senior to staff
A contractor's schedule risk analysis claims a 92 % chance of meeting your deadline. You see that every pessimistic estimate is the most likely value plus 10 %, and that no two activities are correlated. How do you judge the claim?
- What it tests
- Recognising anchored, narrow ranges and missing correlation, knowing their effect on the result, and asking for an analysis that can be trusted.
- First step
- Compare a few of the ranges with history: how far did similar activities actually overrun on past projects? A uniform +10 % is a sign that the ranges were derived from the plan, not estimated.
- Follow-ups
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- Why does missing correlation make the result too optimistic?
- What would you ask the contractor to change?
- What confidence would you expect after the changes?
From the lesson Three-point estimates and schedule risk analysis
Model answer, Pro.In the answer:
- Model answer
- Follow-up answers
- Common mistakes
- Rubric
- Variants
- about 2 minutes
All Project Management & Agile interview questions · The Project Management & Agile track