After The Pareto Game, which had more than 3000 people playing and discussing the outcomes, we now have another one – The Fishbone Game. To ensure participation from everyone, I need to begin with the basics. In case you have significant expertise in problem solving, please be patient or consider moving directly to “Start Quiz” and “The Game”.
Drawing a fishbone diagram requires asking “Why?” as many times as necessary to try and reach the roots of a problem. Also known as cause and effect diagram, why-why analysis or the five why analysis, this approach is often used to analyze problems systematically. To check the effectiveness of why-why analysis, some experts propose that we should be doing the reverse “therefore” check. Let us try this once with an example. In a company, HR folks were doing why-why analysis for poor selections in a recruitment drive. One cause for fewer than expected selections was poor pass ratio in the mandatory written test. This had happened because the majority of candidates did not write the test. Our why-why analysis looks like this –
- Why were number of selections below expectations?
It was so because very few candidates passed the mandatory test.
- Why was it that very few candidates cleared the written test?
This happened because only 10% of the candidates wrote the mandatory test.
We can continue like this to go deeper and find sub-causes. At the end, we may like to do the “therefore” test which begins at the lowest root (sub-cause) level. The “therefore” statement for this example so far goes like this – Only 10% of candidates wrote the test, therefore, very few students passed the test and therefore, very few were selected. Let us examine this statement. Was writing the test a necessary condition to pass the test? Yes, it was. Was it a sufficient condition to pass the test? No, it was not. If more people had written the test, we do not know if more would have cleared. Possibly, the uninterested or the weaker one’s escaped the test. We are unsure about the cause being right because the condition of writing the test was necessary but not sufficient for passing the test.
Necessary Condition – A condition is necessary if absence of the condition guarantees absence of the effect.
Sufficient Condition – A condition is sufficient if presence of the condition guarantees the presence of the effect.
The real question now is – Is this discussion about the cause (or a set of causes) being necessary and/or sufficient really important? What is its exact role in problem solving?
I hope you have got six out of six in the quiz. Let us bring our focus back on cause and effect analysis. In the following questions, please choose your preferred option and see how it compares with others.
Question 1 – X is an identified cause for Y and Y is a negative undesirable effect. Is the following statement True or False? –
It is possible that X is neither necessary nor sufficient for Y to occur.
Question 2 – X is an identified cause for Y and Y is a negative undesirable effect. Is the following statement True or False? –
In the quest to permanently eliminate Y, if X is found to be sufficient for occurrence of Y, we should consider just X as our focus area; X being necessary does not really matter.
Question 3 – X is an identified cause for Y and Y is a negative undesirable effect. Is the following statement True or False? –
If X is found to be sufficient for occurrence of Y, it means that X must also be necessary for Y.
Question 4 – X is an identified cause for Y and Y is a negative undesirable effect. Is the following statement True or False? –
If X is necessary for Y, this means that the occurrence of Y is sufficient to prove that X has happened.
Question 5 – X is an identified cause for Y and Y is a negative undesirable effect. Is the following statement True or False? –
To permanently eliminate Y, the following must happen – We must be able to target and address a set of X’s, which is necessary as well as sufficient for Y to occur.
The effective use of Fishbone or the Why-Why analysis depends on the kind of causes we identify or get satisfied with. This tool requires many other techniques in conjunction for solving complex problems. It is important to remember that this tool forms the starting point for many analyses, and we need to begin in the right way. In a complex problem solving sequence like DMAIC, we need to redraw our Why-Why analysis several times. Just as starting right is important, it is crucial to know when to end our cause analyses. Much of it depends on asking the right questions. Necessity and sufficiency form a part of such questions.