5.11 Project Management Tools: Gantt Charts, Toll-Gate Reviews, WBS, and RACI

Four tools, four questions

Work breakdown structure

A WBS decomposes the project into a hierarchy of deliverables -- nouns, things that get produced -- not activities. This distinction is the most-tested feature. "Validated measurement system" is a WBS element; "run gage R&R" is an activity that produces it.

Two governing rules:

• The 100% rule. The children of any node account for exactly 100% of the parent's scope: nothing missing, nothing extra, no overlap. If the children do not sum to the parent, the decomposition is wrong.
• The work package level. Decompose until each lowest element can be estimated, assigned to one owner, and tracked. A common heuristic is the 8/80 rule: a work package should take between 8 and 80 hours.

Example extract for a DMAIC project:

1.0 Measure phase
    1.1 Operational definitions
        1.1.1 CTQ measurement definitions
        1.1.2 Defect classification rules
    1.2 Validated measurement system
        1.2.1 Variable gage R&R report
        1.2.2 Attribute agreement analysis report
    1.3 Baseline data set
        1.3.1 Data collection plan
        1.3.2 Collected and cleaned data
        1.3.3 Baseline capability report

The WBS is the backbone of everything else: schedule estimates attach to work packages, RACI rows are WBS elements, and progress is measured as work packages completed rather than as effort expended.

Gantt charts

A Gantt chart plots tasks as horizontal bars against a calendar, showing start, duration, finish, dependencies, milestones, and often percent complete and resource assignment.

Dependency types

Finish-to-start dominates DMAIC work.

Critical path and float

The critical path is the longest sequence of dependent tasks through the network; its length is the shortest possible project duration. Total float (or slack) is how long a task can slip without delaying project completion. Tasks on the critical path have zero float, so any delay there delays the whole project.

Worked example. Four tasks: A (10 days) then C (15 days); B (8 days) then C. C is followed by D (5 days).

• Path A-C-D: $10 + 15 + 5 = 30$ days.
• Path B-C-D: $8 + 15 + 5 = 28$ days.
• Critical path is A-C-D at 30 days. Task B has $30 - 28 = 2$ days of total float.

The practical use is triage. If the project is late, adding resource to task B changes nothing; compressing A or C is the only option. Two compression techniques: crashing (adding resource to critical tasks, which raises cost) and fast tracking (running sequential tasks in parallel, which raises risk).

In DMAIC projects the critical path very often runs through data collection -- you cannot compress four weeks of production data into one week -- which is why data collection planning deserves front- loaded attention.

RACI

A responsibility assignment matrix maps WBS deliverables against people.

Three diagnostics you should be able to run on a RACI:

• Two A's on one row: nobody is accountable; the decision will stall.
• No A on a row: the deliverable will not be completed.
• Too many C's: every consultation is a delay; if someone only needs to know the outcome, they are I, not C.

Note that on the control plan row, the process owner is Accountable, not the Black Belt. That assignment is the whole point of the Control phase: accountability transfers.

Toll-gate reviews as a tracking tool

Toll gates belong in this list because they are the mechanism that converts progress into a decision. The other three tools tell you where the project is; the toll gate decides what to do about it. The governance detail is covered in the charter review section; for project management purposes the key point is that a milestone on a Gantt chart is a date, whereas a toll gate is a decision with criteria, and only the latter can stop a project that should be stopped.

Using them together

1. Build the WBS from the phase deliverables.
2. Estimate duration and dependency for each work package, and build the Gantt from it.
3. Identify the critical path; protect it and front-load data collection.
4. Assign RACI at the deliverable level, one A per row.
5. Set toll gates at phase boundaries with written entry criteria.
6. Track completed deliverables against the Gantt, not hours spent, and revise at each gate.