Root Cause Methods

the contributing causes with one of the cause categories given in Appendix A (also available through a

HELP screen).

A number of methods for performing root cause analysis are given in the references 3 through 17.

Many of these methods are specialized and apply to specific situations or objectives. Most have their own

cause categorizations, but all are very effective when used within the scope for which they were designed.

The most common methods are:

Events and Causal Factor Analysis

Change Analysis

Barrier Analysis

Management Oversight and Risk Tree (MORT) Analysis

Human Performance Evaluation

Kepner-Tregoe Problem Solving and Decision Making.

A summary of the most common root cause methods, when it is appropriate to use each method,

and the advantages/disadvantages of each are given in Figure 2 and Table 1. The extent to which these

methods are used and the level of analytical effort spent on root cause analysis should be commensurate

with the significance of the occurrence. A high-level effort should be spent on most emergencies, an

intermediate level should be spent on most unusual occurrences, and a relatively low-level effort should be

adequate for most off-normal occurrences. In any case, the depth of analysis should be adequate to

explain why the occurrence happened, determine how to prevent recurrence, and assign responsibility for

corrective actions. An inordinate amount of effort to pursue the causal path is not expected if the

significance of the occurrence is minor.

A high-level effort includes use and documentation of formal root cause analysis to identify the

upstream factors and the program deficiencies. Both Events and Causal Factor Analysis and MORT could

be used together in an extensive investigation of the causal factor chain. An intermediate level might be a

simple Barrier, Change, or Mini-MORT Analysis. A low-level effort may include only gathering

information and drawing conclusions without documenting use of any formal analytical method. However,

in most cases, a thorough knowledge and understanding of the root cause analytical methods is essential to

conducting an adequate investigation and drawing correct conclusions, regardless of the selected level of

effort.

Events and Causal Factor Analysis is used for multi-faceted problems or long, complex causal

factor chains. The resulting chart is a cause and effects diagram that describes the time sequence of a

series of tasks and/or actions and the surrounding conditions leading to an event. The event line is a time

sequence of actions or happenings while the conditions are anything that shapes the outcome and ranges

from physical conditions (such as an open valve or noise) to attitude or safety culture. The events and

conditions as given on the chart describe a causal factor chain. The direct, root, and contributing cause

relationships in the causal factor chain are shown in Figure 3.