When solving problems the first thing a person needs to understand is where they are starting from. To do this they have to create a baseline. A set of data for the current process and situation. Without a baseline, a person will never know if they improved the process or made it worse.
When I say a baseline, I mean an understanding of data of the current situation. I do not mean a range of what is considered normal. A range does nothing but tell a person where they might expect the data to fall when creating a baseline under normal conditions. A range can hide problems under the guise of being acceptable. What if something is at a high end of an range and drops to a low end of the range? This can still create problems.
For example, two parts have to fit together. If both parts are at the high end of the range of their part variation they snap in perfectly. Then one part drops to the low end of the range, while the other is at the high end of the range. Now the parts don’t fit together and people are confused because both parts are within their acceptable range. The issue is there never was a baseline created to understand both parts were at the high end and this condition created a good result.
The area I have the most frustration with this is in health care. A person can go to the doctor wondering if they have hearing loss or damage. The doctor tests you and says you are fine there is no damage or loss. How do they know? They never had a baseline from before to understand the person’s hearing is any different. The doctors just tells the person they are fine because they are in the “normal” range.
The assumption is the range is built on lots of data over time and covers the 80-85% of the normal distribution of data, again assuming the data fits a normal distribution curve. What if the person is someone at one of the extremes of the curve? Doesn’t this change things?
I understand doctors need some tools to help them out. That is what a range is a tool. If a patient says something is not normal for them, the doctor can’t say they are normal because their test falls in a certain range.
Ranges are nice and can be helpful, but they are not a substitute for a baseline. The baseline gives a more detailed picture. Baselines help to problem solve and improve. So before judging if there is a problem, a person should ask, “Where did I start from?” or “What is my baseline?”