PPP Manual - Exercise 2 Critical Path Method

1 PERFECT PROJECT PLANNINPERFECT PROJECT PLANNINPERFECT PROJECT PLANNINPERFECT PROJECT PLANNINGGGG ADVANCED PROJECT ADVANCED PROJECT ADVANCED PROJECT ADVANCED PROJECT MANAGEMENTMANAGEMENTMANAGEMENTMANAGEMENT Perfect Project Planning Page 1 of 5 Exercise 2 Critical path Method February 2009 Exercise 2 Critical path Method In this Exercise we reproduced the exact network of Tasks that Stephen Devaux uses in the opening chapters of his book, Total Project Control. You should understand the Critical path Method thoroughly. There isn't much to it. I suggest trying to explain it in just a few words to someone who hasn't ever heard of it.

2 If you can't do it, you need to think about it some more. The Bricklaying Exercise , although addressing many of the Scope, Time and Cost principles wasn't suitable to demonstrate the Critical path Method because, with just two Tasks, it doesn't have a network with any alternative paths. Both Tasks were on the Critical path and both Tasks were Critical . Select Tools, go to , and on the View Sheet place a tick against Show Project Summary Task. Click OK. Project 1 will now appear in your Task Name Column. File, Save Type Ex 2 Critical path Method (This will override the Project 1 that appeared in the Task Name) Five Tasks is enough to produce a sample network and therefore more than one possible path .

3 With two alternative paths, one of them must be the Critical path . We saw the effect of changing the Durations of the Tasks so that the Critical path switches from one path to the other. It is also possible to adjust the Durations of the Tasks so that both of the alternative paths have the same overall duration and they are both Critical . PERFECT PROJECT PLANNINPERFECT PROJECT PLANNINPERFECT PROJECT PLANNINPERFECT PROJECT PLANNINGGGG ADVANCED PROJECT ADVANCED PROJECT ADVANCED PROJECT ADVANCED PROJECT MANAGEMENTMANAGEMENTMANAGEMENTMANAGEMENT Perfect Project Planning Page 2 of 5 Exercise 2 Critical path Method February 2009 Create the above table, Step 1: Enter your Task list first, Step 2: Allocate the duration of each task.

4 Step 3: Link your tasks (refer Exercise 1) this was done directly by entering the ID number in the predecessor column. You can have more than one predecessor put a comma between the id numbers. Or hold the Ctrl key down on the predecessor and select the successor then release the Ctrl key and select the link option from the toolbar Highlight the Critical path , Step 1: Select Gantt Chart Wizard from the toolbar Step 2: Next, Select Critical path , Finish, Step 3: Format it. Exit Wizard. There will be more on Formatting in Exercise 10. Change the duration of the tasks and the Critical path can change. We used the Schedule Table (View, Table, and Schedule) so that we could see the: Early Start (ES) Late Start (LS) Early Finish (EF) Late Finish (LF) PERFECT PROJECT PLANNINPERFECT PROJECT PLANNINPERFECT PROJECT PLANNINPERFECT PROJECT PLANNINGGGG ADVANCED PROJECT ADVANCED PROJECT ADVANCED PROJECT ADVANCED PROJECT MANAGEMENTMANAGEMENTMANAGEMENTMANAGEMENT Perfect Project Planning Page 3 of 5 Exercise 2 Critical path Method February 2009 Free Slack Total Slack The early dates, Early Start and Early Finish (ES, EF), are calculated by the Forward Pass.

5 The late dates, Late Start and Late Finish (LS, LF) are calculated by the Backward Pass. The ES, EF, LS, LF, or rather the difference LF-EF or LS-LF, then give the Free Float and Total Float (MSP calls them Free Slack and Total Slack) Free Float is amount of time by which the Task can be delayed before it delays another Task. Total Float is the amount of time by which the Task can be delayed before it delays the project finish. ES EF LS LF PERFECT PROJECT PLANNINPERFECT PROJECT PLANNINPERFECT PROJECT PLANNINPERFECT PROJECT PLANNINGGGG ADVANCED PROJECT ADVANCED PROJECT ADVANCED PROJECT ADVANCED PROJECT MANAGEMENTMANAGEMENTMANAGEMENTMANAGEMENT Perfect Project Planning Page 4 of 5 Exercise 2 Critical path Method February 2009 The Critical path Method is characterized by: A fixed Start Date but no other dates, or Date Constraints.

6 Tasks scheduled to start as soon as possible. Resource limitations not a factor. Scheduling forwards from a Start Date (NOT backwards from a finish date). Tasks linked by their Predecessor relationships and Lag. A path , or more than one path , made up of the Task Durations and the Predecessor links. The Critical path is the longest path through the project network and determines the shortest possible overall project Duration. Tasks on the Critical path are the Critical Tasks. Non- Critical Tasks have Float. Critical Tasks have zero Float. If Critical Tasks are delayed, the project finish date is delayed. If Critical Tasks can be shortened, or if Critical Tasks can be moved off the Critical path , the Project Finish Date will be earlier.

7 In order to control the project schedule and the project finish date it is necessary to direct limited effort and resources at the Critical Tasks, , the ones that matter. The Critical path can change during the course of project execution, as actuality unfolds. Tasks will Start and finish earlier and/or later than planned, and will have longer or shorter durations than estimated. If a Non- Critical Task is delayed long enough, the delay will consume the entire Float and the Task can become Critical . Therefore, it is necessary to monitor and track progress continuously in order to identify the Critical Tasks and the Critical path continuously.

8 Although the Critical path Method identifies the earliest possible project finish date, this is only an essential starting point and not necessarily an appropriate target date or contract finish date. In a real, practical project planning situation, there must be further allowances for the inevitable Resource limitations and uncertainties that will arise in the course of project execution. However, modeling the project accurately in order to find the Critical path and the earliest possible start and finish dates is an essential first step. It often happens that the project finish date as determined by the Critical path is later than some "target" finish date or a "contract finish date".

9 This might be bad news but at least it is valuable information about the project feasibility, and the scale of the problem that you must solve, that you may not have had otherwise. These PERFECT PROJECT PLANNINPERFECT PROJECT PLANNINPERFECT PROJECT PLANNINPERFECT PROJECT PLANNINGGGG ADVANCED PROJECT ADVANCED PROJECT ADVANCED PROJECT ADVANCED PROJECT MANAGEMENTMANAGEMENTMANAGEMENTMANAGEMENT Perfect Project Planning Page 5 of 5 Exercise 2 Critical path Method February 2009 target/contract finish dates are usually externally imposed and are arbitrary to the extent that they have nothing to do with how long the project takes or the shortest duration that is possible.

10 However, they cannot be ignored entirely. (How to record these dates will be covered in a later Exercise ) The process has an input side and an output side. You should take care to be able to distinguish between input and output. If the outputs from the Method are in some way not acceptable, the only recourse is to go back and adjust the input side of the equation. You must find a way to shorten the Duration of Critical Tasks or get them off the Critical path entirely. You should study the basics of the Critical path Method and be able to describe it, and its features, characteristics and uses, in simple terms. The Critical path Method is not complicated, but it is very important.