The Psychology of Quality and More
Process Decision Program Chart (PDPC)
The Process Decision Program Chart (often just called PDPC) is a very simple tool with an unnecessarily impressive sounding name, possibly derived from the Japanese name, from where it came as one of the 'Second seven tools (also known as the 'Seven tools for management and planning').
How does it work?
A useful way of planning is to break down tasks into a hierarchy, using a Tree Diagram. PDPC simply extends this chart a couple of levels to identify risks and countermeasures for the bottom level tasks, as in the diagram below. Different shaped boxes are used to highlight the risks and and countermeasures (they are often shown as 'clouds' to indicate their uncertain nature).
Is that all? Well, yes and no. Yes, that is what the diagram is used to show. No, identifying risks and countermeasures is not all that easy and seldom done that well. Often, when the plan is complete, you are raring to go and are not keen on stopping to think about what might go wrong. That might make you feel a bit uncomfortable, and after all, what do they pay you for? Managers must manage. If problems occur, you will handle them as they appear.
But unfortunately, problems almost inevitably do occur, and when they do they are often in areas that could have been easily identified if a little forethought had been applied. Using PDPC is going slow to go fast, using a little rigour to identify possible problems and countermeasure in each area before diving into action.
How do you do it?
1. Break down the task into a Tree Diagram. The bottom 'leaves' on the tree will now indicate the actual tasks to be carried out.
2. For each bottom-level task 'leaf', brainstorm or otherwise identify a list of possible problems that could occur.
3. Select one or a few of the risks identified in step 2 to put on the diagram, based on a combination of probability of the risk occuring and the potential impact, should the risk materialise.
4. For each risk selected in step, brainstorm or otherwise identify possible countermeasures that you could take to minimise the effect of the risk.
5. Select a practical subset of countermeasures identified in step 4 to put on the chart.
6. Continue building the chart as above, finding risks and countermeasures for each task. If there are a large number of tasks, you can simplify the task by only doing this for tasks that are considered to be at risk or where the impact of their failure would be alarge.
An example of PDPC used witha cutting machine is shown below.
PDPC also works well in a text hierarchy, where you can use any combination of indenting and numbering to show the depth of each item. The example below shows risks and countermeasures in italics. X's and O's are also used to show rejected and selected countermeasures.
2.0 Milling of casting master
2.1 Put design detail into computer
2.1.1 Miskeyed detail
O 22.214.171.124 Use same computer format as design software
X 126.96.36.199 Key twice for verification
2.2 Produce machine control tape
2.3 Mount tape
2.4 Clamp raw casting block into milling machine
2.4.1 Wrong material
X 188.8.131.52 Spectral analysis
O 184.108.40.206 Visual check in process notes
2.4.2 Wrongly clamped
O 220.127.116.11 Train operator
2.5 Run machine to compete milling
Key: O = Selected countermeasure
X = Rejected countermeasure (too expensive, difficult, etc.)
Next time: The Gantt Chart
This article first appeared in Quality World, the journal of the Institute for Quality Assurance
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