Complexity Increases Sigma Values

If most of the industry operates at 3-sigma (66,000 defects per million) per process what is the effect of multiple processes. When a patient goes through a process there are almost always multiple steps that can have an error. Each step is going to have it’s own sigma value. Remember that in health care a defect is any error that causes the patients course of treatment to be altered. Only one step needs to be in error to cause the patient’s course to be changed. Remember the old punch line “the operation was a success but the patient died”.

The sigma values of steps, therefore, are cumulative not independent. The chart below shows how “accurate” or error free a multi-step process is. It’s obvious that the more steps the process has the harder it is to achieve an overall sigma of six-sigma.

So when reviewing a process for patients one the initial steps when mapping the process and looking at accuracy is to determine whether a step can be eliminated. Not only will it cut down on wasted time but it will improve the accuracy of the process exponentially.