Adonis Diaries

Error taxonomies

Posted on: October 4, 2008

“What are error taxonomies and the other kinds of taxonomies in HF?” 

(April 9, 2005)


Would you please give me a minute to set the foundations first?

Friend, may you allow me just a side explanation on experimentation? 

Psychologists, sociologists and marketing graduates are trained to applying various experimentation methods and not just cause and effect designs.

There are many statistical packages oriented to providing dimensions and models to the set of data dumped into the experiment so that a preliminary understanding of the system behavior is comprehended qualitatively.

Every applied science has gone through many qualitative models or schemas, using various qualitative methods, before attempting to quantify their models.

Many chairmen of engineering departments, especially those who have no understanding of the disciple of Human Factors and would never touch this body of knowledge and methods with a long pole, ask me to concentrate my courses on the quantitative aspects.

That hint sends immediate shiver through my rebellious spirit and I am tempted to ask them what taxonomy of methods they use in teaching engineering courses.

What taxonomies Human Factors have to conceive?  How about the classification of human errors when operating a system, their frequencies and consequences on the safety of operators and system performance?

Human Factors professionals attempted to establish various error taxonomies, some within a specific context during their study and analysis of the errors that might be committed in the operation of nuclear power plants and others that are out of any specific context.

One alternative classification of human errors is based on human behavior and the level of comprehension; mainly skill-based, or rule-based or knowledge-based behavioral patterns. This taxonomy identifies 13 types of errors and discriminate among the stages and strength of controlled routines in the mind that precipitate the occurrence of an error whether during execution of a task, omitting steps, changing the order of steps, sequence of steps, timing errors, inadequate analysis or decision making.  With a strong knowledge of the behavior of a system, provided that the mental model is not deficient then applying the rules consistently most of the errors will be concentrated on the level of skill achieved in performing a job.

Another taxonomy rely on the theory of information processing and it is a literal transcription of the experimental processes; mainly observation of a system status, choice of hypothesis, testing of hypothesis, choice of goal, choice of procedure and execution of procedure.  Basically, this taxonomy may answer the problems in the rule-based and knowledge–based behavior.

It is useful to specify in the final steps of taxonomy whether an error is of omission or of commission.  I suggest that the errors of commission be also fine tuned to differentiate among errors of sequence, the kind of sequence and timing of the execution.

There are alternative strategies for reducing human errors by either training, selection of the appropriate applicants or redesigning a system to fit the capabilities of end users and or taking care of his limitations by preventive designs, exclusion designs and fail-safe designs.

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October 2008

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