PERT and critical path

A PERT chart shows activities and dependencies as a network rather than as bars, which makes the critical path visible: the sequence with no slack, where any delay is a delay to the whole project.

It is the diagram to draw when someone asks what would actually happen if a task slipped.

#When to reach for one

• Schedule risk analysis before committing to a date.

• Explaining why one task matters more than three others.

• Comparing plans, where the critical path differs between options.

#How to draw it in Capable

#A worked example

Activities, durations, and a critical path in bold:

The source, which you can paste into a new diagram and edit:

digraph pert {
  rankdir=LR;
  node [shape=box, fontname="Helvetica"];
  edge [fontname="Helvetica", fontsize=10];
  start [shape=circle, label="Start"];
  end [shape=doublecircle, label="End"];

  start -> design [label="5d"];
  design -> build [label="15d", penwidth=3];
  design -> content [label="8d"];
  build -> test [label="10d", penwidth=3];
  content -> test [label="2d"];
  test -> launch [label="3d", penwidth=3];
  launch -> end;
}

#A few things that catch people out

• Slack is the useful number. Tasks with slack can absorb delay; tasks without cannot.

• The critical path moves when estimates change. Recalculate rather than trusting last month's diagram.

• Three-point estimates (optimistic, likely, pessimistic) are the original point of PERT and still useful.

#Related

A plan you can change is a plan people trust.