The Five Whys is a guideline suggested by Masaaki Imai for troubleshooting problems. It was made popular as part of the Toyota Production System (1970’s.) Application of the strategy involves taking any problem and asking “Why – what caused this problem?” Then, when we learn what caused the problem we ask the same question again. The strategy, as commonly understood, is to ask “Why” five times (more or less) uncovering links in a causal chain until we have uncovered the “root cause” of the problem.

Purpose.The lion’s share of the benefit to learning the Five Whys strategy is the increased likelihood that we will look past the presenting problem to learn more about how that problem came into being. This understanding helps us to develop good corrective actions. and to improve our systems.

Cause Analysis. For each step of the Five Whys strategy we ask why and record our answer. But, whenever we are unable to answer the question, it is an opportunity to apply a cause analysis tool to determine the cause and thereby uncover another link in the causal chain.

What tool? To determine the cause of a problem we have a range of options: from simply asking an expert to determine the cause for us, to using a trial & error procedure, to using a design-of-experiments analysis, or better yet, using the BPI cause analysis thinking process. The point is that cause analysis comes into play during application of the Five Whys strategy when we ask why and are unable to answer immediately and with complete confidence.

Tip? Next, we have found that even experts in problem analysis often fail to appreciate the precise meaning of the words they use. For example, the term “root cause” should not be taken to mean “the last link in the causal chain.” It should be interpreted to mean “the network of elements (below the surface) that taken together produced the problem (on the surface)” – a root not a root tip.

The analogy with a “root” breaks down somewhat when we realize that how far back (down below the surface) we go in our search for causal links is up to us. The root never really stops. (Why Daddy? Why? Why?. . .) So, we must decide when we know enough and move on to considering what corrective action to take.

The advantage to conceptualizing cause as the entire root structure (rather than just the tip of a root) is that this provides more options to consider. By considering a wider range of options, we are better assured of an optimal solution.