The Critical Path Method

• read the narration column first
• then do the exercises

Reading list

You do not need to consult all these books. If you can find one in your local library, concentrate on that author.

• David M. Stires, Maurice M. Murphy, Modern management methods PERT and CPM : program evaluation review technique and Critical Path Method, Boston Materials Management Institute 1963
• John Stanley Baumgartner, Project management, Homewood, Ill. Irwin 1963
• Albert Battersby, Network Analysis for Planning and Scheduling, London Macmillan 1979
• Joseph J. Moder, Cecil R. Phillips, Project management with CPM and PERT, New York Reinhold 1983.

1. The staff of a large high school decides to hold an ‘original poetry’ competition . The event is meant to promote student interest in literature, so the winners will be selected by a panel chosen by the students themselves. You have been asked to organise the event.

1. List the component elements of the preparation.
2. Draw up a scheme.
3. Analyse the ‘critical path’ - from point of view of the time element and importance factor.
4. Did you find the exercise enlightening?

narration

3.1 Understanding the concept of a ‘critical path’

The science of management has developed the so-called ‘critical path method’. It is a way of analysing the various activities involved in a project and the most efficient way of completing them. To use another image: if you are carrying luggage on a journey, you will want to find the shortest and easiest route.

For the construction of a house, for instance, basic building materials have to be procured, such as steel, bricks, concrete and wood. Meanwhile preparations must be made for certain specialized work that will have to be done in one or other particular phase of the building, such as masonry work, installing the electrical equipment, fitting the frames for the doors and windows, laying the waterpipe and sewage system, and similar jobs. A number of firms may be involved. Certain parts of the work cannot be done before others have been completed. All this requires a coordinated plan in which the various activities have to be linked in such a way as to finish the building within the shortest period and with the maximum use of the available personnel.

The ‘critical path method’ deals with this type of planning. The method may best be explained at the hand of detailed examples. Most students will be familiar with the organizational background of seminars and so we may well take this as our starting point.

Suppose that a conference or seminar is planned for teachers from various districts of a region. How is it to be organised? Common sense may tell us that finding the right speakers, or fixing the correct date, or locating a good venue, may be the most crucial factor, depending on our circumstances. But such a haphazard approach might make us overlook other problems or opportunities. How to go about it systematically?

Step 1. Listing component activities

First we set about distinguishing the activities that go into the preparation of our seminar. They could amount to the following:

• A. Attracting speakers for the main talks.
• B. Sending circulars to find out on what date a maximum of response could be expected, (i.e. to fix the most suitable date for the seminar).
• C. Raising some initial funds to finance the seminar.
• D. Finding suitable accommodation, once the date has been determined, and making provisional bookings.
• E. Making provisional arrangements for the catering.
• F. Sending final information to the participants, requesting them to confirm their attendance and to provide information regarding their arrival and desired transport for departure (for travel arrangements).
• G. Photocopying the texts which speakers may have prepared.
• H. Making the final arrangements for accommodation in the light of the precise data regarding the participants.
• I. Making the final arrangements with regard to the catering.
• J. Winding up the final preparations in the line of supplying material for the meetings, etc.
• K. Booking return transport for certain participants etc.

Such a list does not do justice to all aspects of the preparation. Which activity presupposes another one? What should be done first, what later? And we will also need to calculate the length of time we need to complete the various preparatory activities for our seminar.

How do we go about it?

Step 2. Drawing a diagram

To see how the activities relate to each other, in causal sequence and in duration of time, we need to express the activities in a scheme such as that found in the figure printed below.

The capital letters in the scheme refer to the activities listed. Each letter is attached to a line (an arrow) which signifies the path which this activity has to run through time. With the letter the estimated minimum duration of the activity has also been indicated. A (attracting speakers) will have to be begun at least four months months in advance (will take 120 days). Sending the circulars (B) will require at least a month to produce the necessary response from. the teachers, after which the date can be fixed and the provisional arrangements made (D and E). Collecting the confirmations and final information from the participants again requires at least a month (F). Only after this information is known can the final arrangements (H.I.J.) be made. These, however, would only require about a week each. It is different for the travel arrangements for some participants which have to be seen to at least fifteen days before the seminar (K). It should be noted also that the speakers: have to send the same final information (presumably with their draft) before the last arrangements can be made (therefore A and F meet in the same point). Moreover, the financial preparation must have been realized to some degree at the same time (that is why C concurs with A and F).

So far the explanation of the scheme. But what is its use?

Step 3. Analysing the diagram

The diagram, first and foremost, gives us a clear picture of the minimum time required to prepare for the seminar. Let us have another look at the scheme:

The work of contacting and receiving commitments from the participants (the line running through B, D and F) will only require two and a half months. But raising funds (C) requires three months and booking good speakers (A) four months in advance. During the first period of the preparation, therefore, the ‘critical path’ runs through A and so we may conclude that this period will require a minimum time of four months.

The second period begins when all the final information from speakers and participants has been collected. The last arrangements of stencilling, providing equipment, finalizing accommodation and catering would not take more than seven days: But it is foreseen that the booking of return travel will require fifteen days. In the second period, the ‘critical path’ runs consequently through K.

In general we may, therefore, conclude that the ‘critical path’ runs through A and K and that the total minimum duration of preparation amounts to four and a half months.

The scheme is also helpful in other ways. Knowing the time required for A (the critical path).we can be somewhat more generous in setting the deadlines for activities B, D and F. We can also clearly distinguish the activities that are done parallel and which can be easily shared out to different cooperators. This is especially true for the second period when activities G, ,H, I, J and K could be executed by various persons and groups. Another advantage lies in the adjustments we will have to make when it turns out that certain activities take more time than expected in the schedule. In all these aspects the advantages are the greater, the more detailed and specific our preparation is and the more clearly we have succeeded in expressing it in a comprehensive scheme.

To determine the critical path, we list the activities, express them in a scheme and analyse the implications.

Imagine you are a surprise birthday party for a friend or colleague in your own home.

How does the ‘critical path method’ apply here?

3.2 Finetuning

One can also analyse a programme with a slightly different accent. Let us imagine that we have to produce a brochure on an institution or movement we belong to.

The following activities could be listed as coponent elements in such a project:

• A. Formulating the concept of what should be con tained in the pamphlet.
• B. Formulating the concept of what should be ex pressed on the front cover.
• C. The actual writing of the text by a recognized author.
• D. The drawing of the cover picture by an artist.
• E. The reviewing of the text in the light of the proposed concept and in the light of the desired style and readability.
• F. Choosing the title of the pamphlet.
• G. Acquiring approval of relevant authorities or leaders for the proposed text.
• H. Commissioning the illustrations for the cover page.
• I. The printing and proof reading of the booklet.

The relationship between these activities could be expressed in terms of intermediate events, which we call milestones. On the figure below we have tried to make the connections visual, admitting at the same time that a different sequence would be possible.

As in the previous figure we have symbolized the activities by arrows and labelled. them according to the capital letters attributed to each in the list. The ‘milestones’ have been expressed by small circles.

Reading the scheme one may understand how after the formulation of the concept (A), the author can write (B), submit his text for review (E) and obtain approval (G).

Simultaneously the design for the cover page (B) can have been worked out by an artist (D), and after the title has been determined (F), the illustration can be made (H). Here both lines (of text and coverblock) converge, so that a beginning can be made with printing (I) accompanied by proof reading (J).

The time element of this scheme is difficult to fix beforehand. , it is important that the process should move on as fast as possible, to prevent unnecessary delays.

To achieve this the general editor may keep some activities in his own hand (such as formulating the concepts (A, B), fixing the title (F) and the proofreading (J). For the other activities he depends on specialists : the author (C), the artist (D), the language reviewer (E), the censor (G), the blockmaker (H) and the printer (I).

To achieve a maximum of efficiency the editor will have to have at his disposal a choice of alternative cooperators for each of these specializations. This is all the more required if he needs to produce not just one, but a whole series of brochures in his programme. Experience will show him where bottlenecks are likely to occur: with the authors, the artists, the printers, etc. and for these specializations he will therefore have to attract more cooperators.

In such kinds of programming one should note that there are three basic elements that make up its composition: (a) time; (b) resources (personnel, finance, etc.); (c) the activities. There is a basic rule of efficiency that states that each of these three elements can be determined if the other two have been fixed.

For instance, if we know the activities that are involved in the bringing out of a pamphlet (c) and we can determine with precision the resources (personnel and finance) at our disposal (b), we can calculate the time it will take to produce it (a).

If the time element becomes so important that we want it to be reduced to a minimum (the brochure must appear within three days), then we achieve this by raising the resources (personnel, finance) to a maximum.

Or again, suppose that we have been given a certain time limit (a) and we have a very restricted promise of resources (b), then our activities towards the production will have to be regulated accordingly (we might have to omit a picture on the cover, etc.). Real efficiency will be achieved if we make use of all. three elemts to our greatest advantage.

The ‘critical path’ method has many applications in everyday organization. It is a technique that may require some time before we have learned to handle it swiftly and with ease. But if we accustom ourselves to adopt it, it will certainly prove a great help to us in every stage of our planning.

Solving

Research

Path

Strategy

Image

Face to Face

Consulting