Variation

Every process contains variation. No two ways of performing a task are always the same. People have their own styles, their own interpretations of a process, and their own ways of carrying out the process. Some variation is normal, expected, and cannot be changed. This normal variation can actually be measured. Variation outside of the range of what is considered normal, also known as "abnormal" variation, needs investigation. It is this type of variation within a process that makes it difficult to successfully implement change. Abnormal variation must be identified and either eliminated if a "bad" variation, or incorporated into the process if found to be beneficial.

It is also important to understand "normal variation". For instance, when measuring door-to-balloon time with an average of 90 minutes, the measured times will not all be 90 minutes. Some may be 80 minutes and some 110 minutes. This does not mean that the staff with the 80 minute timeframe does a better job than those with 110 minutes. These time differences may all be part of the normal variation based upon a 90 minute average. A control chart will help identify both normal and abnormal variation.