… or Defending Categorization
(an excerpt from a draft of the revised TapRooT® Book
available later in 2007, Copyright © 2007)

Some cause-and-effect gurus object to use of the TapRooT® System’s Root Cause Tree® because they feel that any categorization restricts the thinking of an incident investigator. They maintain that the only way to ensure a complete, unbiased, unbounded root cause analysis is to attack each problem from the viewpoint of basic engineering and human performance principles and let the evidence lead where it may by the use of cause-and-effect, deductive reasoning, and testing of hypotheses. Our extensive investigation research and development as well as basic psychological principles show that this thinking is wrong.

The deductive reasoning and “hypothesis proving” used in fault trees, 5-Whys, and cause-and-effect actually cause problems that we will explain in this article. We will explain how these problems are solved by the tools used in the TapRooT® System. For TapRooT® Users, this article supplies the evidence you need to defend the good practices that TapRooT® and the Root Cause Tree® are based on when you are faced with the argument that “categorization” is a problem.

TapRooT® and the Root Cause Tree® have extensive testing and field use that proves the Root Cause Tree® does not limit the thinking of investigators. Just the opposite is true. Once an investigator is trained in using TapRooT®, they find a broader range of causes – they are less restricted in their thinking – than before they were trained in the use of TapRooT®. This is true even if they were previously trained in using a cause-and-effect based root cause analysis system.

Why, when using TapRooT®, do analyst find causes that they would have previously overlooked? There are several reasons.

First, when using TapRooT®, investigators use tools in addition to Root Cause Tree®. These tools that are used before using the Root Cause Tree® encourage a better collection of information before the root cause analysis begins. SnapCharT® is especially helpful for organizing investigation information and spotting missing or conflicting information. Equifactor®, CHAP, Change Analysis, and Safeguards Analysis are excellent tools to help the investigator understand what happened before they start analyzing why it happened. Thus when using TapRooT®, investigators are often better prepared to find root causes and less likely to jump to conclusions than they are when they use systems based primarily on cause-and-effect (which doesn’t have these built in information collection tools).

Second, very few investigators have the broad knowledge, training, and experience in all of the fields needed to use cause-and-effect to analyze a complex accident. What kind of knowledge and experience would be needed? A short list includes: equipment engineering, maintenance, operations research, management theory, human factors, ergonomics, and training theory. Therefore, most people need guidance to direct them to the wide variety of Root Causes that should be considered when investigating a problem. They get this guidance when using TapRooT® and the Root Cause Tree®. We have not seen this level of high quality guidance in any other system.

Third, even experienced gurus fall into a common trap. They develop “favorite cause-itis”. The concept of “finding the answer you want” has been proven by independent research. Thus, experienced investigators have a tendency to ignore information that does not fit their hypothesis and look for information that confirms their hypothesis. This tendency is called a confirmation bias. A short list (of thousands) of research papers from the past 40 years that confirm the existence of a variety of types of confirmation bias, and the effects of confirmation bias to many fields, include:

Thus, experienced investigators trying to confirm a hypothesis (the method used when building a fault tree or implied in the deductive reasoning used in most applications of 5-Why’s and cause-and-effect), will not have an “unbiased analysis” that they hope to achieve by avoiding categorization. Instead, they need a system (like the Root Cause Tree®) that focuses on a broad spectrum of possibilities. They need to use facts to select or eliminate the conditions under which the problem occurs (and thus what best practices can be used to eliminate the condition – just like the Root Cause Tree® provides). They need the guidance of the 15 Questions and the Basic Cause Categories of the Root Cause Tree® to make sure they avoid the “favorite cause” confirmation bias trap.

Fourth, almost all thinking is categorical in nature. For example, language is a categorization of certain sounds into standard meanings. Thus, a dictionary of a language is a book of categorized meanings and pronunciations. Thus, someone who opposes the use of the Root Cause Tree® because it is categorical is just replacing one well-thought-out, well-defined set of categories with another set. The new set is the one that they don’t realize that they have in their mind. Often, we have observed that the set of categories in a guru problem solver’s mind is more restrictive (as measured by the variety of outcomes in their investigations) than the categorization presented by the Root Cause Tree®. You can, therefore, think of using the guru approach (with no well thought out categorization) as trying to communicate without a standard language, without a dictionary, and without even having a standard alphabet. Imagine how effective this unstructured communication would be…

Finally, the Root Cause Tree® is not just categorization. The Root Cause Tree® is not a simple checklist. It has an expert system (the 15 Questions, the Basic Cause Categories, and the Root Cause Tree® Dictionary questions) built into it. Thus the problems encountered when using a “pick-list” of root causes have been solved by the structure and expert systems built into the Root Cause Tree®. The comparison of the Root Cause Tree® to a pick-list of root causes is a false comparison. When you see this false comparison used by those who wish to justify the use of other, less well developed, root cause analysis techniques, you will then realize that their system can’t compare to the robust, proven tools used by TapRooT®, including the Root Cause Tree®. Therefore, they have developed a weak straw man to make their system look superior in comparison to a purposefully chosen weak system – a simple pick list.

Our research and experience, in addition to independent research on confirmation bias, shows that the structure and categorization used in the Root Cause Tree® doesn’t need to be apologized for. Rather, the structure and categorization of the Root Cause Tree® is a vast advantage over other non-structured, poorly categorized techniques that don’t have expert systems built into them, such as 5-Why’s, cause-and-effect, and fault trees.

The next time you are asked to defend the Root Cause Tree® versus root cause analysis based on cause-and-effect analysis, fault trees, or 5-Why’s, you will be armed with the facts that show the superior design of the TapRooT® System.

If you would like to see two previous articles on problems with 5-Whys and Fault Tree Analysis, click on the links below…

What’s Wrong With 5-Why’s

What’s Wrong with Fault Trees