While Lean doesn't require many tools other than a pad of Post-it Notes, Six Sigma thrives on charts, graphs, and diagrams of performance data. At the Institute for Healthcare Improvement (IHI) Conference in 2015, Don Berwick asked everyone to recommit to improvement science—control charts, Pareto charts, and histograms of performance. He sounded annoyed with the lack of use of Lean Six Sigma tools and methodologies. I understand his frustration. I was there in 2006 when he asked everyone to "pledge allegiance to science and evidence." Over the years, I've done a stroke tally of the quality tools used in IHI poster presentations. I gave each poster one check-mark for each type of tool used (Figure 7.1).
IHI use of Six Sigma tools.
Sadly, even with all the emphasis on control charts, Pareto charts, and other tools of quality, they are used rarely in poster presentations. The vast majority are Excel line, bar, or column charts. This is like using an old rotary dial telephone instead of a smart phone. Basic Excel charts can't tell you much about your process, but control charts, Pareto charts, and histograms have much needed intelligence about performance.
TREND LINES CAN TELL LIES
I was reading an old issue of the Joint Commission Journal on Quality and Patient Safety. In an article about patient falls, the authors used a run chart with a trend line to assert that they had achieved a 9.9 percent reduction in patient falls (Figure 7.2).
Line graph of patient falls with trend line.
The trend line suggests a trend, but does one exist? If we use an XmR control chart to plot the same data (Figure 7.3), we find that the process is stable and unchanged; the trend line has lied about the improvement. This is why primitive line charts, run charts, and trend lines can be so misleading— they aren't statistically useful. You will need a control chart to detect actual changes in performance.
XmR control chart of patient falls.
The 2015 IHI sessions on high-reliability healthcare (e.g., Memorial Hermann) suggest that zero defects are possible with Lean Six Sigma and change management—basically "improvement science." You cannot get to zero harm without using these tools. To succeed at using Six Sigma to achieve zero harm, you'll need a set of power tools, but you won't need every tool in the Six Sigma toolkit. You will mainly need: