The Psychology of Quality and More
Gantt Chart: How to do it
How to do it
When breaking the work down, aim to find clearly allocable chunks, where the required skills and resources are obvious. The duration of each task should be of comparable length and be short enough to enable clear tracking. For example, in a 12 month project, it is reasonable to have tasks of around 1 week each, whilst a 4 week project may be broken down into tasks which take no more than 1 day.
Each task should be uniquely identifiable, either from its name or an allocated code. A simple scheme is to use a coding structure based on the work breakdown structure. For example, the drawing of a a motor housing in the design phase may be coded as DE.DR.MH01.
Note that at this stage actual resources are not allocated; the information from this step is fixed, whilst actual resources may be shuffled around between tasks.
A tool for matching tasks and people is the Resource Allocation Matrix.
It may become clear at this time or later that there are insufficient resources to complete the project within the required time-frame, necessitating the acquisition of additional resources.
Note that there is a chicken-and-egg situation between resources, estimation and allocation. For example, a skilled person may be initially estimated to take two days to complete a task, but then is found to be over-allocated in later calculations. As a result, a less skilled person is allocated, which changes the estimation to three days, which in turn changes the overall work profile of the project. This may result in several cycles of allocation, estimation and calculation before a satisfactory solution is found.
Independent tasks, which can be performed simultaneously, may be allocated priority values, for example to ensure that higher risk tasks are done earlier.
A table, such as in the Fig. 1. may be used to organize the information from steps 2 to 7.
At a minimum, this will include an identification of each task (name or code) plus the bar for that task. It may also include columns for additional information, typically anything from steps 2 to 8, but most usefully the names of the people who will perform the task, as in the illustration.
The bar for each task will fill each time column (identified in step 8), even if it represents only a part of this time. For example, in the illustration, the bar for 'Design new form' occupies two full day columns, even though it may only take a part of the second day. This potential confusion can be avoided by using the same scale for effort estimates and time columns, although this may result in a large number of columns or very coarse estimates. The best approach is usually to scale the time columns to fit on the page and be careful not to get confused by any task overlap.
Fig. 2. Building the Gantt Chart
This Histogram may then be used to perform load balancing by identifying actions to change tasks, resources, allocations and times that will enable the resources to be optimally used. For example, if a person is allocated to two tasks at one time, then either allocate one task to someone else or move it to a free period.
After doing this load balancing, you may need to go back to step 5, repeating this process until a satisfactory chart is obtained.
Progress on the project can be shown by publishing the completed chart, with a vertical line to show the current date, as in the illustration. All bars and part-bars to the left of the line are completed, and all to the right are yet to be done.
And the big