Improvement Insights Blog
Use Numbers Not Percentages
Ever noticed that when you describe something as a percentage people seem to draw a blank? They may nod, but not understand. Here’s why:
“I want to alert you to something that I discovered when I saw my friend, Dr. Jack ReVelle, speak. Now, if you know anything about control charts, you know that if you have an upper and lower control limit, well, 99.7% of all points should fit between those two things. And I saw Jack talk about this and I realized that nobody can make a picture of a percentage. 99.7%… What the heck does that look like? But Jack said, “What that means is that three points out of a thousand can normally be outside of the control limits in a natural state.”
“So, if you see it within 20 or 30 points, it might be an out of control condition and you should investigate. Three points out of a thousand, people can make a picture of that. All right?
“So, that comes into other things like Pareto’s rule: 20% of what you’re doing is producing 80% of the waste, rework, and lost profits. Well, those are a little bit easier numbers, but still a little hard to understand. And I narrowed that down because within the Pareto, 4% of what you’re doing produces over half the mistakes, errors, waste, and rework, but people still don’t know what 4% is. Right? So I said, well, that’s four steps out of a hundred or one step out of 25. Right? So it’s one step out of every 25 that is causing over half your waste, rework, lost profit, and whatever.
“Now, does this start to give you some ideas? If you’re going to talk about percentages, which no one can make a picture of, can you convert it into a number? Right? Three points out of a thousand. Oh, I know what three points out of a thousand looks like. A little bit, big thing. Right? Does this make sense? And when you start to do that, people can understand it better, quicker, and that leads you into a situation where learning becomes super fast.
“So, that’s my Improvement Insight for this week. Turn percentages into a number. And when you do that, people want to learn more quickly. Let’s create hassle-free healthcare, a hassle-free America. Let’s go out and improve something this week.”