How to Use a Cause-and-Effect Diagram
Known by many names, including the Ishikawa diagram, the fishbone diagram, the sequence-of-events diagram and the fault tree, the cause-and-effect diagram was invented by Kaoru Ishikawa when he was working at Kawasaki shipyards in the 1960s. You can use a cause-and-event diagram to drill down all possible causes for a single event. Ishikawa was dedicated to continual quality improvement and used the fishbone to outline and control for all variables that deter from quality.
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Instructions
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Put together a multidisciplinary project team to examine the completed cause-and-effect diagram. If the cause-and-effect diagram you are examining is about mental health re-admissions, you may want to invite your team's psychologist, psychiatrist, a nurse practitioner, an intake worker, discharge worker and a ward aid to get viewpoints on how to address potential causes identified. The completed diagram will look like a fish skeleton. It will have one organizational failure listed at the head of the fish and the "bones" will each be potential causes of this failure. If the failure is frequent mental health hospital re-admissions, that will be at the head of the fish. The bones would include causes overarching categories such as "hospital-based" and "external." Under the internal category, the sub-bones of the fish may include patient's treatment needs are not adequately addressed, length of stay too short and patient's lack of participation in the treatment plan. Under the external category the sub-categories might include lack of family support, unemployment or life crises.
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Solicit feedback from all members on the team. Choose to identify either two or three main causes or decide to come up with a plan to remediate all causes identified. Use a tool called the "5 Whys" to drill down to root causes by asking "why" repeatedly until you get to a measurable, specific action plan for each. This is a brainstorming session, so more is better.
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Use a tool called FMEA to identify which causes are most important to address if this is the option your team chooses. FMEA stands for Failure Mode Effects Analysis and it is a grid matrix that helps you score each potential cause in terms of effect, severity, ease of remediation and whatever other factors the team deems to be relevant. The team should address the causes with the highest scores.
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Use a cost/benefit analysis to decide if the causes your team wants to address are the ones that are the cheapest to solve or the ones that require the least effort. The cheapest/least effort causes are called the "low-hanging fruit" in Six Sigma terminology. If this is your team's strategy, you would address the low-hanging fruit and then re-evaluate the failure to see what effect your interventions had. For example, if it is easiest to keep people in the hospital for one extra day to formulate a comprehensive discharge plan, you would do this for a month and then reassess re-admission rate to evaluate the effect of this intervention.
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Formulate research hypotheses based on the finished cause-and-effect diagram. If the team feels that lack of family support may be a factor, the researcher may want to start asking all patients about their existing family supports. If this data already exists, as it does in a standard hospital intake protocol, the researcher will want to analyze the data to see if the objective data meet the subjective thoughts of the team.
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Develop an action plan to address causes. The plan should specifically include itemized actions with a specific person targeted to complete each task. The "who, what, when, where and why" question format is helpful here to outline a specific, achievable, time-limited plan. An example would be, "The charge nurse will review each treatment plan for thoroughness, making sure family support is addressed."
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Re-evaluate. Once the plan has been implemented, continue to gather data and assess if your interventions have lowered the readmission rate. If they have not been 100 percent effective, conduct another another cause-and-effect diagram session with your team and repeat the process. This is known as continuous quality improvement.
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