• “Pareto” Misuse

    Many people have built the Bar Chart in figure 1 below and called it a Pareto Chart. Even I in my early years a Quality Engineer created this chart as a “Pareto chart”. But this is NOT a Pareto Chart. It is only a Bar Chart. Why? This is because this bar chart does not show us,…

  • Design of Experiments Examples in Healthcare

    In regard to Design of Experiments applications in healthcare, consider the randomized clinical trial. These are simple Designed Experiments. Usually they are one-factor-at-a-time (OFAT) experiments that attempt to isolate the effect of one drug across a population. Screening experiments would allow the assessment of multiple factors simultaneously with relatively small sample sizes. Since the OFAT…

  • What the Heck is Multicollinearity?

    A Lean Six Sigma Master Black Belt was perplexed by the software’s correlation and regression analysis output. The results were pure nonsense. In addition to regression coefficients that were negative when common sense told him they should be positive (and vice versa), some of the correlation coefficients were large, while the corresponding regression coefficient p-values…

  • Must Six Sigma Be a Panacea?

    The perfect is the enemy of the good, they say. Six Sigma devotees know all about this. Criticisms of Six Sigma are sometimes quite bizarre. Perhaps the most odd are criticisms of what Six Sigma doesn’t do. For example, Six Sigma has been criticized because On the other hand, Six Sigma gets written off too…

  • SPC vs. Knowledge

    Have you ever asked yourself just what control limits actually measure? Oh sure, there are the standard statistical answers: central tendency, process dispersion, capability and so on. But what do control limits measure fundamentally? The answer is ignorance. Ignorance is really the only reason we need SPC, or any statistics for that matter. Statistics help…

  • U.S. Airlines Continue On-Time Improvement in February

    Wow. 83% on time arrivals. And by “on time” we don’t mean, well, on time. On time is defined as within 15 minutes of schedule. This article compares the February on time percentage with January and with February of the previous year. This February was better. Of course, the root cause is assumed to be…

  • Why Isn’t Six Sigma Used More in Healthcare?

    Apparently there are still questions about whether or not a process improvement methodology like lean or Six Sigma can work in healthcare. I find this astonishing and disingenuous. The only real requirement for deploying any process improvement is whether or not there is a process that is done more than once. Healthcare at any respectably…

  • 21 Soft Skills All Six Sigma Belts Need

    One of my most popular articles is 101 Things a Six Sigma Black Belt Should Know. Of course, the list is primarily a list of technical tools and skills needed, but anyone who has worked as a change agent knows that there’s more to it than that. Soft skills are at least as important, if…

  • Small Samples

    What is “Small”? Not enough data. We’ve all been there before. It may be that the production rate is too low. (I’ve worked with processes where one unit per month wasn’t unusual.) It may be that you have many covariates, such as customer research. If you slice-and-dice customers by industry type, geographic region, age, sex,…

  • Nuts-Inspection Won’t Improve Food Safety

    First peanuts, now pistachios. Not to mention spinach, almonds and host of other vegetables. Major salmonella outbreaks have been in the news a lot in recent years. The government and the food industry are working overtime to beef up guidelines on what companies need to do to keep consumers safe. USA Today reports that the…

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