Statistics Article

Jay Arthur—The KnowWare Man’s picture

By: Jay Arthur—The KnowWare Man

When I first learned quality improvement back in 1989 at Florida Power and Light, the consultants who trained us taught a very specific way to draw a Pareto chart. They’d been trained in Japan, the place where quality improvement first took root during the 1950s, so I took it for granted that the way they drew Pareto charts was the authentic and best way to do so.

A Pareto chart combines a bar graph with a cumulative line graph. Using the way we were taught to draw a Pareto chart (figure 1), the bars are touching, making it extremely easy to visually compare levels from one bar to the next. The bars span the entire available space along the x axis. The cumulative line graph springs from the bottom left corner of the first big bar, and each subsequent point is plotted from the corresponding top right corner of its bar.

Ryan E. Day’s picture

By: Ryan E. Day

Current business conversation often focuses on data and big data. Data are the raw information from which statistics are created and provide an interpretation and summary of data. Statistics make it possible to analyze real-world business problems and measure key performance indicators that enable us to set quantifiable goals. Control charts and capability analysis are key tools in these endeavors.

Control charts

Developed in the 1920s by Walter A. Shewhart, control charts are used to monitor industrial or business processes over time. Control charts are invaluable for determining if a process is in a state of control. But what does that mean?

William A. Levinson’s picture

By: William A. Levinson

Anthony Chirico1 describes how narrow-limit gauging (NLG, aka compressed limit plans) can reduce enormously the required sample size, and therefore the inspection cost, of a traditional attribute sampling plan. The procedure consists of moving acceptance limits t standard deviations inside the engineering specifications, which increases the acceptable quality level (AQL) and therefore reduces the sample size necessary to detect an increase in the nonconforming fraction.

Teofilo Cortizo’s picture

By: Teofilo Cortizo

Within maintenance management, the term MTBF (mean time between failures) is the most important key performance indicator after physical availability.

Scott A. Hindle’s picture

By: Scott A. Hindle

‘Process Capability: What It Is and How It Helps,” parts one, two, three, and [Read More]

Tom Siegfried’s picture

By: Tom Siegfried

If Fyodor Dostoyevsky had been a mathematician, he might have written a book called Crime and Statistics. However, since “statistics” doesn’t have quite the same ring as “punishment,” it wouldn’t have sold as well.

David Currie’s picture

By: David Currie

This is part three of a three-part series. Read about good metrics in part one and bad metrics in part two.

Quality Digest’s picture

By: Quality Digest

Annalise Suzuki, director of technology and engagement at software provider Elysium Inc., spoke to Quality Digest about the importance of model-based definitions (MBD) for data quality, validation, and engineering change management. With the increase of digital 3D models in the manufacturing workflow, companies are appreciating their value for speeding product development, improving quality and performance, and allowing for greater automation.

Anthony Chirico’s picture

By: Anthony Chirico

Everybody wants to design and conduct a great experiment! To find enlightenment by the discovery of the big red X and perhaps a few smaller pink x’s along the way. Thoughtful selection of the best experiment factors, the right levels, the most efficient design, the best plan for randomization, and creative ways to quantify the response variable consume our thoughts and imagination. The list of considerations and trade-offs is quite impressive.

Scott A. Hindle’s picture

By: Scott A. Hindle

Walter Shewhart, father of statistical process control and creator of the control chart, put a premium on the time order sequence of data. Since many statistics and graphs are unaffected by this, you might wonder what the fuss is about. Read on to see why.

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