Edelorme 08/11/20181

Testing the explanatory memo on the Pert chart

This is a pre-test exercise based on the explanatory memo on the implementation of the Pert chart.

It deals with the creation of the Pert for the tasks to be carried out between the completion of the logical framework and the finalization of Chapter. 7 of the proposal for the EC.

Here is the table of activities to be used as a basis for the chart:

Code / Description / Duration in hours / Preceding events
A / List of LF activities / 0.25
B / Estimating the duration of activities / 2 / A
C / Identifying the preceding activities / 3 / A
D / Making the post-it game / 0.25 / B A
E / Positioning activity start / 0.25 / D C
F / Positioning finish activity / 0.5
G / Linking start and finish / 2 / E F
H / Estimating time lags / 3
I / Identifying critical path / 1 / H B
J / Explanatory application / 2 / I

The following diagram is obtained

Conclusions following the exercise

Identifying the preceding activities

Generally requires you to identify the result of the preceding activity: Activity B can start when you have obtained the result (the product) of the preceding Activity A.

Plotting the diagramme

The progressive building of the diagramme sometimes entails reviewing (and sometimes correcting) the interconnections between 2 activities initially identified in the activities table.

The most obvious case:

WHICH BECOMES

Identifying the critical path

It would initially be a good idea to calculate the critical path to include the activity durations alone; this provides a starting point.

Next, identify the duration of the time lags (constraints on this path).

Finally, identify significant time lags between activities outside the critical path, which would divert us from the path initially identified.

Duration of the activities and time lags

Durations

As we have to think at a macro level, we need to consider the activities that you have listed as the total interconnected tasks, the duration of the activity being the sum total of the task durations + the sum total of the time lags between the tasks. In fact, we could construct a Pert sub-diagram with its critical path in each activity (circle) (it is the value of this critical sub-path that provides the duration of the activity).

Time lags

In the case of this pre-test, I have identified only one constraint, the tiredness level of the person responsible for producing Chapter 1.7 of the proposal.

When reviewing the critical path and progressively accumulating the activity durations, I have estimated that, after carrying out A, C and E, it was time to eat, that between G and H a short break was required and that, after implementing A, C, E, G and H, it was time to go home to relax and have a good night’s sleep before starting again the following day.

This example to show

That these time lags are not inherent to the implementation of the activities themselves.

And especially the importance of these time lags in calculating the overall duration of the project. If we had taken account only of the duration of the activities in the critical path, ‘A+C+E+G+H+I+J, we may have thought that it could all have been done in 11.5 hours; adding on the time lags; however, we have to add 16.5 hours, which makes 28 hours in all. In order to complete Chapter 1.7 properly, it is therefore more logical to plan for two and a half days, rather than one day.

A few points to remember

This Pert chart is going to have definite effects on the organisation of your time schedule and you must ensure consistency between the two (sequencing of the activities; duration of the activities - representation of the time lags and their duration).

The time lag concept entails identifyingin greater detail the constraints that will weigh on the project, and in particular the constraints imposed bythe Partnership, which we often underestimate.

If you have run out of inspiration identifying the time schedules, have a quick look at the “options” column in the logical framework