The problem with '5 whys'|Tao's Tips

✂ Its popularity is not the result of any evidence that it is effective. ^[1]

The problem is not • how • it is used, but rather that:

it oversimplifies the process of problem exploration
it forces users down a single analytical pathway for any given problem
it insists on a single root cause as the target for solutions
it assumes that the most distal link on the causal pathway (the fifth why) is inherently the most effective and efficient place to intervene

5 whys traces its origin to Toyota Production System: ask why five times whenever there is a a problem … by repeating why five times, the nature of the problem as well as the solution becomes clear. The solution, or the how-to, is designated as 1H. Thus Five whys equal one how (5W=1H).

5 whys a single causal pathway (depth)?

Washington Monument example. ^[1]

Problem: Monument deteriorating.
5W => Midges attracted by the fact that the monument is the first to have the lights turned on at night.
1H => Turn the lights on one hour later.

Comment: The analysis only considers one potential source of deterioration. The first why could just as easily have considered other causes, such as acid rain, erosion from wind, damage from freeze-thaw cycles, or the use of marble as the building material.
Moreover, many of the details were either incorrect, or were never taken into account. For example, tourists were not happy when they wanted to take their photograph at the monument, so the lights were turned back on.

Targeting only the most distal cause (green arrow)

Not only are users of 5 whys limited to one root cause per causal pathway, but they are also limited to selecting only the most distal cause (conventionally, the fifth why). However, there is no logical reason to assume that this is always the most effective or most efficient target for intervention. Actually, if you only choose one place in the pathway to change, it would be best to affect a proximate cause; this could block or diminish the effect of causes more distal to that step.

Figure 2. Green arrow: intervention (counter-measure)

5 whys multiple causal pathways (breadth)!

Another team could easily come up with five wholly different and equally valid whys. And any single string of 5 whys can provide only a blinkered view of the complex causal pathway that led to an incident.

These might include pathways related to a maladaptive workplace culture, clinical and information technology staffing, orientation of temporary staff, and the absence of a forcing function to ensure process steps are implemented. It could also include a focus on improved infection control and better preparedness for infectious disease outbreaks. Solutions based on the 5 whys single causal pathway would leave all of these issues unaddressed.

Lack of a forcing function might include a desire to avoid waking the patient; an unreliable wristband (eg smudged, crinkled or occluded); confusion caused by multiple wristbands; lack of trust in the wristband data due to frequent errors; the lack of a label on the medication or any of a number of other causes.

Systems thinking requires both depth and BREADTH of analysis!

If the 5 whys technique is to be used, it should be expanded into the horizontal dimension; each why starting another causal pathway for the same problem, but different from other causal pathways for that same problem.
However, beware of the potential for users to rely on off-the-cuff deduction and uninformed brainstorming, rather evidence from than experience and observation (EBM) when developing answers and prioritising causes.

Figure 3. Using 5 whys horizontally for independent causal pathways of one of the evidence-based causes [Problem] on a fishbone diagram

So our modified 5 whys technique is now a matrix; horizontally listing the individual causal pathways for a problem, and vertically delving into the step-by-step analysis of root causes along each pathway. Interventions, however, should follow the green arrows and may occur anywhere along the causal continuum and on any causal pathway.

References

Card AJ. The problem with 5 whys BMJ Qual Saf 2017;26:671-677.