Critical Path

Quick reference

• 00:04 Hi, I'm Ray Sheen.
• 00:05 I'd like to talk about a very important element on project schedule planning
• 00:09 on schedule constrained projects and that's the critical path analysis.
• 00:14 The Project Management Body of Knowledge, the PMBOK Guide,
• 00:17 defines a critical path as the sequence of activities that represents the longest
• 00:23 path through a project, which determines the shortest possible duration.
• 00:27 That means that a critical path is the longest, but
• 00:30 not necessarily the most difficult of the project path.
• 00:33 What counts is the duration of time.
• 00:37 Let me show you an example.
• 00:38 This is a simple project network diagram.
• 00:41 There are a total of eight tasks of varying duration and
• 00:44 multiple paths through the network.
• 00:46 Let's look at the length of each of these paths.
• 00:49 If I go along the bottom path, there are three tasks, 2 days each for
• 00:54 a total of 6 days.
• 00:55 If I start in the middle and go low, there is one task of 1 day,
• 01:01 two tasks of 2 days for a total of 5 days, and 3 tasks.
• 01:06 If we follow the middle path, there are three tasks each of 1 day for
• 01:11 a total of 3 days.
• 01:12 And finally, if we follow the top path, there are only two tasks, but
• 01:17 one is 4 days and one is 3 days for a total of 7 days.
• 01:20 This path has the fewest number of tasks, but takes the longest number of days.
• 01:25 Therefore, it is the critical path.
• 01:28 Any delay to the critical path delays the project completion,
• 01:32 since all the other paths will complete before the critical path.
• 01:36 The critical path determines the final end date for the project.
• 01:40 As you might imagine, knowing your critical path is very important on
• 01:44 schedule constrained projects.
• 01:46 Critical path is normally calculated using software.
• 01:50 However, if you intend to sit for the PMP exam,
• 01:53 you should be able to do these calculations manually since you cannot
• 01:57 take any project management software into the test facility.
• 02:01 Let's take a look at how you would go about determining our critical path.
• 02:05 In order to calculate the critical path you must have completed enough of your
• 02:10 project plan to know the relationships between the tasks and
• 02:13 you must have a duration estimate for each task.
• 02:16 This means that you're able to create a network diagram showing all the tasks and
• 02:22 relationships and durations like I had on the previous slide.
• 02:26 If the project is a simple waterfall, meaning you do one task at a time,
• 02:30 the critical path analysis doesn't add much information because there's only
• 02:35 one path in the project.
• 02:36 By definition, that path is the critical path, it's the longest path through
• 02:40 the project since it's the only path through the project.
• 02:45 However, when there are multiple parallel paths,
• 02:48 the critical path analysis will determine which path is the longest and therefore
• 02:52 which path is the one that is constraining the completion of the project?
• 02:56 When the project schedule changes, the critical path might change.
• 03:00 I've been burned by this on a project.
• 03:03 We're focused on the critical path and trying to accelerate it if possible.
• 03:07 We were successful accelerating the critical path, but
• 03:10 another path was delayed and I wasn't watching it closely.
• 03:13 So although the original critical path became shorter,
• 03:16 the actual project critical path had changed and I was managing the wrong one.
• 03:21 The lesson is that when changes occur, recalculate your critical path.
• 03:25 I've said that the critical path information is very important on
• 03:29 a schedule constrained project.
• 03:31 Let's look at how we can use that information.
• 03:34 A good project manager closely manages the highest risk aspects of their project,
• 03:40 whatever those might be.
• 03:41 When the primary project constraint is schedule,
• 03:44 the highest risk aspects of the project is the critical path,
• 03:48 that is the path that will determine when the project will finish.
• 03:51 There is no schedule flexibility on the critical path.
• 03:55 All the other paths have some flexibility to accommodate issues and problems.
• 03:59 Therefore, if a problem occurs on the critical path,
• 04:02 I'll borrow resources from tasks that are underway on non critical paths.
• 04:06 If those tasks are delayed, it does not automatically mean a delay to the project.
• 04:11 But the critical path is delayed the project is delayed.
• 04:15 Another use of the critical path information is when a project is
• 04:19 approaching a major milestone.
• 04:21 I calculate and track the critical path into the milestone.
• 04:25 Often, little hiccups will occur as we approach a milestone.
• 04:29 This critical path calculation helps me to understand the impact and
• 04:33 prioritize the resolution.
• 04:34 Finally, critical path information is used to prioritize any schedule
• 04:39 acceleration techniques.
• 04:40 I apply selected techniques on the critical path in order to accelerate
• 04:45 the end date of the project.
• 04:47 Applying techniques on any non critical path does not help
• 04:50 the project complete any faster.
• 04:53 To accelerate the end of the project, you must speed up the critical path.
• 04:58 >> Understanding which tasks are on the critical path will allow the project
• 05:03 leader and the core team to make better day-to-day project management decisions.

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