Project Management(A6AX 34)

Ourcome3: Planning Tools

Developed from SQA COLEG pack by Margaret Pearson, Lauder College

Aims and Objectives

By the end of this unit you should be able to: • Draw a Gantt chart from a task list • Draw an activity network from a task list • Identify the critical path through the network

and the float time for each task

Planning Tools and TechniquesIn Section 2 you learned how to make task lists, set deadlines, define milestones and allocate resources.

While these are essential constituents of project planning, they will be of little use unless they are documented in a structured way which allows for easy comprehension and rapid updating.

There are a number of tools and techniques available to accomplish this documentation

Simple projects require simple planning tools otherwise more time is spent in controlling the tool than in controlling the project.

Gantt ChartsThese have been available for a long time and involve the use of simple bar charts to plan a project's progress. They are named after their originator Henry Gantt.

A Gantt chart is a bar or line chart which is used to schedule the different tasks which make up a project. Each bar represents a different task and the length of the bar represents the relative length of the task.

For tasks which can be done in sequence, a one-dimensional Gantt chart, which is basically just a calendar, can be used. A two-dimensional Gantt chart is used for tasks which can be performed at the same time.

Who uses Gantt Charts?

Gantt charts are used for the planning and control of any kind of job or project which involves a number of tasks. They can be used by project managers, systems analysts and anyone else involved in the project.

The main advantages of Gantt charts• They are simple to use and should be easily understood by

everyone who needs to look at them.• They are drawn to scale, time-wise i.e. the length of the bar

indicates the relative length of time the task is going to take.

Disadvantages of Gantt charts • The major disadvantage of a Gantt chart is that it doesn't

show task dependence - ie which tasks have to be finished before other ones can be started. In the example you may suspect that tasks D and E start after task B is finished, but the chart does not really tell you this. This is where Critical Path Analysis which you will also learn about in this section has an advantage as it shows the order of precedence.

A Simple Example - Laying a Garden Path Remember we looked at this example in Section 2. First you must list the tasks. I have given them letters to make it easier later on.

TaskA. Order hardcore and asphalt B. Dig up the area of lawn to be replaced by the pathC. Take delivery of the hardcoreD. Take delivery of the asphalt E. Lay the hardcoreF. Lay the asphalt G. Roll the asphalt H. Re-seed the area of lawn on either side of the path

Now add durations.

A

B

Task

O rder hardcore and asphalt

D ig up the area of law n

Duration

1 day

2 days

c

Take delivery of the hardcore

0 .5 days

D Take delivery of the asphalt 0 .5 days

E Lay the hardcore 1 day

F Lay the asphalt 2 days

G R oll the asphalt 1 day

H R e-seed either side of the path 0 .5 days

Next determine the dependencies, ie the order of tasks

Task Preceding Tasks

Duration

A O rder hardcore and asphalt 1 day

B D ig up the area of law n 2 days

c

Take delivery of the hardcore 0.5 days A

D Take delivery of the asphalt 0.5 days A

E Lay the hardcore 1 day A, B, C

F Lay the asphalt 2 days A, B, D

G R oll the asphalt 1 day A, B,C , D , E, F

H R e-seed either s ide of the path 0.5 days A, B, C , D , E , F ,

G

Activity 19

Laying the Path:Draw a Gantt chart of the project. You might like to use squared paper for this activity, but you can probably manage with lined or plain paper and a ruler. You will have to make some assumptions for this activity.

Answer to Activity 19 on previous page

I have assumed that I can't take delivery of both the hardcore and asphalt at the same time. Perhaps because I have to shovel it off the same bit of pavement.

I have also assumed that I can order the hardcore and asphalt at the same time as I dig up the lawn, someone else might be doing the hard work while I phone around for prices etc.

Your chart may look a little different from mine if you made different assumptions.

Network AnalysisNetwork analysis is a planning technique used in projects. It involves a complex inter-relationship of activities such as Research and Development, Design and Maintenance work. The process involves breaking the project down into manageable steps: • Establishing a sequence of jobs and drawing a diagram specifying

the inter-connection between them.

• Estimating a timetable for the start of each job.

• Analysing the spare time on each job and thus isolating the most critical jobs.

The two well-known network analysis techniques are PERT (Project Evaluation and Review Technique) and CPM (Critical Path Method).

The two well-known network analysis techniques are PERT (Project Evaluation and Review Technique) and CPM (Critical Path Method). • PERT was developed by the US Navy Special Projects Office to

plan and control the Polaris project. Since this was a top priority US weapon, it was scheduled to be ready at the earliest possible date, regardless of cost or resource limitations. PERT was designed to control the duration of a project.

• CPM was developed by an Operational Research group in industry. Naturally, therefore, it was aimed towards cost minimisation. The CPM approach is that a job should be completed at a specified time with minimum costs.

Basic Techniques Network analysis can be broken down into three phases: PlanningThe jobs in a project are drawn up in a feasible sequence . A diagram is drawn showing the inter-connection (represented by an arrow) between them.

SchedulingA timetable is established, showing start and finish times for each job.

AnalysisThe occurrence of float (spare time) on a job is analysed. As a result jobs on the critical path are isolated.

Network Diagrams

A project is represented by a network diagram, often called a PERT diagram in which each activity, or task, is shown as a box or 'node'. The boxes are linked by arrows that represent the direction of dependency. The work progresses in the direction of the arrows, usually from left to right across the page.

Job A must be completed before Job B can start.

A B

Job A m ust be com pleted before either Job B o r Job C can s ta rt.

Jobs A and B m ust be com pleted before Job C can start.

A c

B

B A

c

A suggested sequence of steps when using this technique as part of the planning process is: • Identify and list tasks to be done.

• Identify and list dependencies between tasks. • Draw draft network.

• Add estimates for the duration of tasks.

• Analyse network identifying the critical path.

• Use as a basis for resource allocation.

Drawing a PERT Diagram

There are several different conventions you can use when drawing a PERT diagram. All must show the basic four elements:

Label for the task - Name or other identifying text.

Duration of task - Estimate of the amount of time to complete in days/weeks/months.

Earliest start time - Earliest time the task can possibly start.

Latest start time - Latest time the task must start to ensure the schedule does not 'slip'.

Example - Building a BoatMay Day is a lone yachtswoman who intends to build a boat to sail round the world. We are going to draw a PERT diagram to schedule a project to build the 'Saucy Sue'.

Listing the tasks and durations, and determining the dependencies, gives us the table below.

Task Duration Preceding Tasks

A F itting the D eck B Raising the sail c Laying the keel D Planking the sides E Launching the boat K Fitting the rigging G Raising the m ast H Painting the name I Varnishing the deck

4 days 1 3 3 1 2 1 1 5

C,D A,C,D,F,G

c A,B,C,D,F,G,H,I A,C,D,G A,C,D C,D A,C,D

Draw A Draft NetworkThis network is made up of the tasks and their dependencies. For example tasks G and I cannot start until task A is complete. Tasks B, H and I all have to be complete before task E can commence. The node representing a task is divided into four quarters. The name of the task (or letter here for simplicity) goes in the top right quarter of the node.

Activity 20

Add durations to the network

Draw or photocopy the draft network I have drawn. Add durations to the tasks. The duration goes in the bottom right quarter of the node.

Answer to Activity 20 on previous page

Analyse the Network

You have to pass through the network calculating the earliest times tasks can start and the latest times tasks must start then identify the critical path.

Activity 21

Add The Earliest Start TimesAssume a start time of day 0 for the earliest task. Calculate the earliest start time (EST) for each succeeding task using the formula:

EST = EST of previous task + duration of previous task

So that means the EST of task D is day 3, as the previous task (C) has an EST of 0 and has a duration of 3 days..

Where two or more paths join, the latest EST is taken as all tasks have to be complete before the succeeding task can start. This is the case for task E. You will have to work out the EST three times (from tasks B, I, and H) and take the biggest answer as the EST for task E.

I have started this activity for you. Complete it and then turn to the next page to compare your network with mine

Answer to Activity 21 Note that the EST for task E can be worked out from task B which gives an answer of day 14, from task I which gives an answer of day 15 and from task H which gives an answer of day 7. The correct answer is day 15 since even if you have raised the sail and painted the name, you cannot launch the boat until you have finished varnishing the deck.

Calculate The Earliest Finish Time

EFT = EST of last task + duration of last task

In this case the earliest time the project can finish is day 16

Activity 22

Calculate the Latest Start Times

Calculate the latest start time (LST) for each task. This is the trickiest part of your analysis.

Pass through the network from finish to start. Subtract the duration of a task from the LST of the succeeding task. In the case of the last task, subtract the duration from the Earliest Finish Time. The float (spare time) is the difference between the LST and EST.

I have started this activity for you. For task B, I have subtracted its duration of 1 day from the LST of its succeeding task, task E, which is 15 to give an LST of day 14 for task B.

Where there is more than one possible answer, you take the lowest answer. This is the case for tasks D and A.

Answer to Activity 22 on page 21Note that there are two answers for the LST for task A. Subtracting its duration of 4 days from 11,the LST of task G, gives an LST of 7. Subtracting its duration from 10, the LST of task I, gives an LST of 6. You take the lower answer, 6, to be the LST of task A.The two answers for the LST of task D are 3 from task A, and 11 from task H, so you take 3 as the LST of task D.

Activity 23

Calculate the Latest Start Times

Calculate the latest start time (LST) for each task. This is the trickiest part of your analysis.

Pass through the network from finish to start. Subtract the duration of a task from the LST of the succeeding task. In the case of the last task, subtract the duration from the Earliest Finish Time. The float (spare time) is the difference between the LST and EST.

I have started this activity for you. For task B, I have subtracted its duration of 1 day from the LST of its succeeding task, task E, which is 15 to give an LST of day 14 for task B.

Where there is more than one possible answer, you take the lowest answer. This is the case for tasks D and A.

Answer to Activity 23The PERT chart is updated as the project progresses and actual durations, or more accurate estimated durations are entered. The critical path can change in the course of a project. The project manager concentrates his/her attention on the critical path tasks and may divert resources to prevent these tasks slipping, i.e. taking longer than the estimates. Remember any slippage of the critical path tasks causes the whole project to slip.

Advantages of Critical Path Analysis

Attention can be concentrated on the most critical jobs.

Spare time can be used to advantage, i.e. spread over other jobs.

Resources can be balanced.

Project completion dates may be brought forward.

Revision of plans can be simplified.

SummaryYou have come to the end of Section 3. You should know how to schedule a project using Gantt charts and PERT diagrams.

This section should have given you the underpinning knowledge you need to use project management software to schedule projects in Section 4.