CAPM Predictive Domain: WBS, Critical Path and the Variance Math Behind 17%

Predictive, Plan-Based Methodologies is Domain II of the CAPM, at 17% of the exam. That works out to about 23 of the 135 scored questions, by Passy's arithmetic, so it is the smallest domain. It is also the only one whose enablers name calculations. PMI's CAPM Examination Content Outline (2023 Exam Update) names exactly three calculations for it: critical path methods, schedule variance, and cost variance. Everything else in the domain is about knowing when a plan-based approach fits and which plans and artifacts keep it under control.

The three predictive tasks in PMI's CAPM outline

The task names are shortened from PMI's outline. Two outline rules apply here as everywhere: enablers are illustrative examples, not an exhaustive list, and predictive, adaptive and business analysis approaches appear across all four domains. A predictive idea such as change control can turn up in a Fundamentals or Business Analysis question too.

PMI's 2023 Exam Update FAQ says the exam includes concepts from both the PMBOK Guide Seventh Edition and Process Groups: A Practice Guide. For this domain, the process-focused title is usually the more direct match, because process groups, work breakdown structures and schedule development are process topics. The CAPM PMBOK 7 or 8 guide explains how the reference lists fit together.

When a plan-based approach fits, and what "each process" means

The outline asks you to judge fit but doesn't give the answers. A practical reading, which is Passy's guidance rather than PMI's, is that a predictive approach suits work where requirements are clear and stable, change becomes expensive once work starts, and a contract or regulator fixes the scope. Building, hardware installation and regulated reporting are typical examples.

Organizational structure changes the picture rather than deciding it:

"The activities within each process" points to the five process groups that process-based references use. The typical activities below are Passy's summary:

"Project components" usually means the building blocks of the plan: phases, deliverables, work packages, activities and milestones. A question may ask which one a given item is. A milestone marks a point in time, an activity consumes time, and a work package is the lowest level of the WBS.

WBS and work packages on the CAPM

A work breakdown structure breaks the total scope of the project into smaller deliverables, level by level. Its lowest level is the work package, a piece of work small enough to estimate, schedule, assign and control. Two conventions are worth knowing: the WBS includes all the project's work and only that work (often called the 100% rule), and a WBS dictionary describes each element in detail. Activities for the schedule are then derived from the work packages. These descriptions are Passy's summaries of common practice.

A fictional community garden project, broken down to work packages:

Notice that the WBS lists deliverables, not a sequence. Order and timing come later, in the schedule network below.

Critical path the CAPM way: list the paths

The garden's schedule has six activities, with durations in working days and finish-to-start links:

For a network this small, listing every path is the fastest method:

The critical path is the longest one, A–B–D–F, so the project takes 15 days, and its activities have zero total float. For an activity off that path, total float is the critical path's length minus the longest path that runs through the activity:

• C sits on paths of 13 and 11 days, so its float is 15 − 13 = 2 days
• E sits only on the 11-day path, so its float is 15 − 11 = 4 days

A forward and backward pass gives the same result (C: late start 4 minus early start 2), and it is the method to use when a network has too many paths to list. The published PMP critical path guide works one through, along with crashing and fast tracking, which the CAPM outline doesn't name.

A natural follow-up question is what a delay does. If C runs 3 days late, it uses its 2 days of float and pushes the finish out by 1 day, to day 16. Path A–C–D–F becomes 16 days long and is now the critical path.

Cost and schedule variance: the formulas the CAPM outline names

Variance compares earned value (EV), the budgeted cost of the work actually done, with two other numbers at the same status date: planned value (PV), the budgeted cost of the work scheduled by then, and actual cost (AC), what the work done has cost.

A fictional warehouse lighting retrofit with a budget of $80,000 reports, at the end of week 6: PV = $40,000, EV = $36,000, AC = $33,000.

• SV = $36,000 − $40,000 = −$4,000: $4,000 worth of planned work hasn't been done yet
• CV = $36,000 − $33,000 = +$3,000: the work done so far cost $3,000 less than its budget

So the project is behind schedule but under budget for the work completed. One check catches most mistakes: EV always comes first. If you subtract EV from something, the formula is backward.

Which CAPM formulas to know, and which are extras

PMI publishes no formula sheet for the CAPM. This split is based on the outline's wording:

Because enablers aren't exhaustive, the indexes are cheap insurance: in the lighting example, SPI = 0.90 and CPI = 1.09 (rounded), which say the same thing as the variances in ratio form. The forecasts take longer to learn and aren't in the outline, so put them last. If you want them anyway, the published PMP earned value guide covers the full set with a worked example. For drilling the named formulas, step-by-step math for critical path and variances is planned for full CAPM prep, which isn't on sale yet.

Quality and integration plans in CAPM predictive questions

"Apply a quality management plan" means using the plan the project already has: its quality standards, how work will be checked, the metrics, and who does what. In the garden project, if the plan says each bed is inspected against the drawing before planting, a bed that fails inspection is recorded, fixed and re-inspected. It isn't waved through to protect the schedule.

PMI's outline uses "integration management plan" without defining it. In process-based references, integration means coordinating all the subsidiary plans into one project management plan and handling changes across them, usually through one integrated change control process. In a question, that looks like a requested change being assessed for its effect on scope, schedule, cost, quality and risk together before anyone approves it.

Predictive artifacts to recognize on the CAPM

Task 3 asks you to identify predictive artifacts. The outline doesn't list them; these are common ones, with Passy's one-line purpose:

A useful contrast for the exam: in a predictive project, change enters through a change request and change control. In an adaptive project, new work usually goes into the backlog for the product owner to order. The CAPM agile frameworks guide covers that side.

Original Passy practice: three predictive questions

Written by Passy for practice, not PMI items. Questions 1 and 2 use the garden and lighting examples above.

1. In the garden network, clearing the ground (C) takes 3 days longer than planned. What happens to the project finish?

• A. Nothing, because C isn't on the critical path
• B. It moves 1 day later, to day 16
• C. It moves 3 days later, to day 18
• D. It moves 2 days later, to day 17

Key: B. C has 2 days of total float, so a 3-day slip delays the finish by 1 day. A ignores that float can run out. C treats C as critical from the start. D confuses the 2 days of float with the delay to the finish.

2. A project reports SV = −$5,000 and CV = +$2,000. Which statement is correct?

• A. Behind schedule, and under budget for the work performed
• B. Ahead of schedule, and over budget
• C. Behind schedule, and over budget
• D. On schedule, because the two variances partly cancel out

Key: A. A negative SV means less work is done than planned, and a positive CV means that work cost less than budgeted. The two measure different things, so they never cancel.

3. On a predictive project with an approved scope baseline, the client asks the team to add a new report. What should happen first?

• A. Add it if the team has spare time this week
• B. Log a change request, assess its effect on scope, schedule, cost and risk, and send it through change control
• C. Refuse, because the baseline is fixed
• D. Add it to the product backlog for the product owner to order

Key: B. Baselined scope changes through change control. A bypasses it, C ignores that baselines can be changed through the agreed process, and D describes the adaptive route, which doesn't fit a baselined predictive project.

Calculation slips are easy to repeat without noticing, which is why Fix It, planned for full CAPM prep, keeps each missed question until you get it right.

A short CAPM predictive study block

The CAPM study time guide gives this domain about 11 hours of a 64-hour plan. One way to spend them:

Start with the three predictive items in Passy's 20 free CAPM practice questions, which include a critical path and a variance question with worked explanations. For more volume once it launches, 374 predictive questions and 92 flashcards are planned for full CAPM prep.