How often do we get sidetracked by several possible causes of an adverse or unexpected outcome?

In the course of doing a fair bit of process improvement work over the years, one of the really successful strategies I have used is to get people to distinguish between the real cause of an unwanted outcome, and something that has no impact. Put like that it seems pretty simple, but it is almost always more complicated, and serves as a core of the “5 Why” lean tool, always requiring hands on knowledge of the way things work, and usually some data. Ask yourself “Why” successively, up to 5 times, as in this lovely story of the Lincoln memorial and pigeons.

Is the intermittent crushing of boxes by the box erector in the factory caused by a marginal variation in the dimensions of the carton flat (prior to erection) or by the wearing of the bearings in the box erector itself, leading to sloppy operation in one of the clamps? Pretty easy to mistake which of these is the real cause of the stoppages, and waste time trying to fix something that perhaps does not need fixing, while the boxes continue to be crushed.

This is of course different from the confusion about which is cause, and which is effect. I was in the Sydney CBD  last week, and saw several blind people with Labrador dogs. Does having a Labrador cause blindness?