4.2.2 Identifying possible causes
The possible causes of a problem can be written onto Post-it notes or similar, and arranged on a flipchart or whiteboard in the form of a ‘fishbone diagram’. This can be a useful method to help a group to examine causes of problems, and perhaps also to clarify your own thoughts. Figure 4 shows a fishbone diagram produced by Midway Airlines to analyse the causes of delayed flight departures.
To construct a fishbone diagram, you begin by writing the problem in a box on the right-hand side. Next you draw in the backbone and some ribs, each of which should have a heading denoting the area it addresses, such as:
process, procedures or method;
Such headings give the process some structure, but are not essential. If the problem is clearly located within the people area, for example, you could use the ribs of the fish for the main reasons, asking the question ‘Why is the problem occurring?’ Each of these reasons could then be split into sub-reasons, by asking the same question again.
1. Think of something that recently went wrong at work. Draw this out as a fishbone diagram, tracing each contributing factor back to the causes of the problem. Keep asking, ‘Why did this happen?’ until you are sure that you have identified all of the contributing causes.
2. What can you do to prevent this problem from recurring? Consider each cause that you have identified, and what could be done to prevent a similar problem arising again.
You may like to discuss your diagram and your suggestions for solutions with your manager or the team who encountered this problem. It may be helpful to draw up the diagram with others who experienced the problem because, if they are involved in analysing the causes, it is likely to be easier to engage their support in implementing solutions.
When the possible causes are laid out like this, the structure helps to show duplications and links between them, so that you can eliminate any that do not apply. Causes on more than one arrow may be significant, and could be described as primary causes.
Fishbone diagrams help break down an issue into more manageable pieces, encouraging the team to escape from the cage of linear thinking and generate new ideas. Possible solutions may begin to emerge for even the most intractable problems if these are looked at in this different way.
Using data collected over one month, Midway Airlines constructed a histogram illustrating how many times each cause of delay had arisen (Figure 5: Histogram of Midway Airlines flight departure delays). Using the Pareto principle, which says that 80 per cent of a problem is generated by 20 per cent of the causes, helps to identify priorities for action.
Using this histogram, identify the main causes of flight departure delays.
The histogram showed that the main causes the airline should concentrate on were:
acceptance of late passengers;
waiting for pushback;
waiting for refuelling;
late weight and balance sheet.
All other causes added together only contributed 11.7 per cent to the total.