I've become a big fan of the "5 Whys" investigation technique and now include it in my investigation training sessions. It's a question/answer technique that looks at the cause/effect relationship of a particular problem.

Here's an example. A worker looses the tip of his finger when it's pinched between a drive belt and an unguarded pulley. The first step is to identify the problem. In our case it's self-evident. Continue to ask WHY about each response to a question and when you are no longer able to answer the question you've likely arrived at a root cause.

1. Why was the worker's finger crushed?

His finger was caught between a moving pulley and belt.

2. Why was the finger caught between the pulley and the belt?

The guard on the pulley was missing.

3. Why was the guard missing?

A mechanic had overlooked replacing it.

4. Why was it overlooked?

There is no written equipment servicing checklist.

5. Why is there no checklist?

No hazard assessment has been completed.

While it's called the 5 WHYS, the exact number of WHYS are not cast in stone. In the above example we would have likely kept the questioning going to find out why no hazard assessment was completed. Whatever the answer was would be considered a root cause.

The greatest benefit of the 5 WHYS is that it engages people and fosters communication between investigators. The process is simple, there are no tables, menus, charts or books to follow. It gets to the root cause quickly, effectively and inexpensively. It's a process that fits well with other root cause methods and in particular, the report forms you may already be using. I find it's a great starting point and it gets new investigators over the apprehension of having to identify causal factors from a menu of dozens on the root cause portion of their company investigation report; as they now understand the immediate, basic and root causes.

There are some legitimate criticisms of the process, but most of these deal with using the process to solve complex or technical problems. I believe an investigation team comprised of experienced front line workers will pretty much identify a correct root cause 99% of the time.

Another criticism is that it tends to get to just a single root cause, and others may be overlooked. I think this is a real possibility, but also one easily fixed. In the above example, had we determined that not only was the guard missing, but the worker was involved in horseplay, then we would simply need to start two streams of questioning. One set of 5 WHYS for the missing guard and the other set for horseplay.

Searching the web for "5 WHYS" will produce lots of hits. Here's one with a good overview of the process.

The Five Whys Technique -- Asian Development Bank

Investigation Kit

Kit Details (pdf article)

Pricing and Ordering Information

E-Learning Programs

My E-Learning programs are available without cost to newsletter subscribers. Each takes about an hour to complete.

Incident Investigation
The Incident Investigation program provides an overview or introduction to the process.

Collision Scene Management
The Collision Scene Management session would benefit drivers who may have to gather collision scene evidence.

Alberta Occupational Health and Safety Act

Convictions - Alberta Occupational Health and Safety Act

Charges - Alberta Occupational Health and Safety Act