Critical Decision Method


An extension of the critical incident technique, the critical decision method (CDM) utilizes cognitive probes in semistructured interviews to elicit information about how experts formulate their decisionmaking strategies.


To generate knowledge for the development of expert systems, develop training materials and identify requirements, and determine the effect of expert systems on task performance.

How do I use this tool?

1. DEFINE THE TASK OR SCENARIO UNDER ANALYSIS. Typically, the focus will be on nonroutine, emergency, or extreme incidents.

2. SELECT CDM PROBES. The CDM method utilizes probes to elicit knowledge from subject-matter experts (SMEs). The purpose is to gain insight into the decisionmaking process the SMEs undergo during critical points in the incident being analyzed. The probes should be defined before the analysis is conducted to prevent irrelevant or non-compliant information. If no pre-existing probes are found, analysts can develop their own based on the needs of the analysis.

3. SELECT APPROPRIATE PARTICIPANT. After identifying the scenario to be analyzed and the probes that will be used, select appropriate participants. Normally, the SMEs are primary decision makers within the scenario you are analyzing.

4. GATHER AND RECORD ACCOUNT OF THE INCIDENT. The CDM can be used for incidents which were observed by the actual analyst or for incidents that are described from memory by one of the participants involved. If performing a CDM analysis on something that is observed, simply observe the incident and then record the observed account. If recalling from memory, the analyst performing the CDM must obtain a description of the incident from the SME, from beginning to end.

5. CONSTRUCT INCIDENT TIMELINE. After an account of the incident is gathered, a timeline of the incident can be constructed. The goal is to provide the analyst with an accurate view of what occurred, including the time and duration of each event. The timeline should include details of both physical events (e.g., alarms going off) and cognitive details (i.e., what the person being interviewed thought and perceived while the incident was occurring).

6. DIVIDE THE INCIDENT INTO KEY PHASES OR DECISION POINTS after it is certain that the analyst has a cogent understanding of the incident. Normally this is completed alongside the SME, and the incident is divided into four or five phases.

7. USE CDM PROBES TO QUERY PARTICIPANT DECISIONMAKING. The analyst should delve into each incident phase identified in step 6, using the CDM probes that were selected during step 2. This should be completed using the probes in the context of an unstructured interview - the goal is to determine the SMEs decision making process within each phase.

8. TRANSCRIBE INTERVIEW DATA from audio recording once the interview is completed.

9. CONSTRUCT CDM TABLES by displaying the CDM probes with their associated answers in a tabular format.

Expertise Required
Users of this tool usually have some training or experience in its use.
Recommended Supplies/Materials
Audio recorder

Can gain specific insight into decisionmaking strategies used by experienced participants within complex and dynamic systems.

Is popular and has been utilized across numerous domains.

Method is normally not time consuming to apply.


Much training, experience, and expertise is necessary to get the most out of the CDM technique.

The skill and experience of the analyst and the quality of the participant can influence the output data from the CDM interview.

Data are dependent on a verbal account of the incident. It is questionable how closely these accounts actually represent the cognitive process of the decisionmaker.

Where can I go to learn more?

Stanton N, Salmon P, Walker G, et al. Cognitive task analysis methods. Human factors methods: a practical guide for engineering and design. Great Britain: Ashgate; 2005. p. 77-108.