Root Cause Analysis Tip: Don’t Follow Bad Root Cause Analysis Advice
I saw two articles by Ronda Levine recommending “5-Whys” as a preferred root cause analysis technique and giving a 5-Why example. Here’s the example from the article:
After determining that the quality management project would focus on the cause of the image bleed on the t-shirts (because almost 2/3 of the t-shirts produced by her company show this defect), Brenda begins to ask “why” to determine the cause of the problem. At the top of a sheet of paper, she writes “2/3s of t-shirts produced bleed through the material from a severity range of barely noticeable to highly noticeable.”
Underneath this, she writes, “Why?”
“The t-shirt fabric is too thin.” This first response can’t be possible, because the company carefully researched the fabric and the ink for the project to ensure the materials would work. So, she looks for an alternate cause and comes up with:
“The ink isn’t drying fast enough.”
“Why not?” She asks the question, again, to get closer to the root cause of the problem.
“Because the presses are using too much ink.” If this is the answer, it would also solve another problem the company has been experiencing, the blurring of images printed on 1/3 of all shirts produced.
Another potential problem at this stage could be that the ink ordered wasn’t correct for the project. However, Brenda checks the inventory logs and finds that this isn’t the case.
“But why are the presses using too much ink?”
“Because the presses haven’t been properly calibrated.”
It seems as though this last answer is a contender. Brenda sits down with her project team and constructs a plan for changing the calibration on the machines.
Seems like this 5-Why example only has three whys. And is “the presses haven’t been properly calibrated” really a root cause? Seems like a Causal Factor (and just a single Causal Factor at that) in TapRooT®.
It seems like a better approach would have been to draw a generic SnapCharT® for the printing, quality control, and delivery process and then analyze all the Causal Factors rather than just one. But you would have to be TapRooT® Trained to understand how this process would work.
I left a comment at the posting referring people back to some of the previous articles I’ve written. Like this one:
http://www.taproot.com/content/2009/08/26/more-bad-root-cause-analysis-advice/
I hate to be so negative, but if somebody doesn’t point out bad advice, many will start using 5-Whys thinking that it is a good idea. Therefore, I’m going to keep pointing out this “BAD ADVICE” until everyone knows the problems with 5-Whys and Cause-and-Effect.
