Tag: Supp.6

OM in the News: The Meningitis Scare and Acceptance Sampling

My family has been closely following the news of the recent meningitis outbreak caused by a contaminated steroid Methylprednisolone. The drug is injected for the treatment of acute back and leg pain. The Centers for Disease Control (CDC) reports 21 deaths and 257 people infected in 16 states from the steroid. Some 14,000 patients, including my sister-in-law, have received such contaminated injections and are in danger of contracting meningitis during the coming months.The specialty pharmacy, New England Compounding Center (NECC),  had the products tested at an independent lab, which in May stated that samples from a batch of steroids were “sterile.”

But The Wall Street Journal (Oct.25, 2012) reports that the sample size that was tested was too small to be meaningful and didn’t comply with industry guidelines. The Oklahoma City testing lab had examined just two 5-milliliter vials of the NECC drug, and found them to be both sterile. The vials came from a batch of 6,528  implicated by the CDC.

Drug makers and compounding pharmacies routinely have their drugs tested by labs as a quality-control measure. Industry experts say such testing can never completely rule out contamination unless every vial in a batch is tested, which is economically impractical. In the case of the NECC steroids tainted with fungi, the size of the testing sample—two vials—is much smaller than the industry standard for the test; for a batch of more than 6,000 vials, the lab should have tested at least 20. And one  drug-testing laboratory quoted in The Journal typically asks for double the number of samples called for in the US standards. “If they’re only testing two vials out of a batch of 6,000, the chances of finding a contaminated vial are very small. Half the batch could be contaminated, and you’d never find it,” says the firm.

For a test to detect contamination with 95% confidence, 18% of the batch would have to be tested, adds a Bristol-Myers executive. “You cannot test quality into a product. You’ve got to manufacture a product in a controlled way and only then does the testing mean anything”.

Discussion questions

1. Ask your students to read Supplement 6’s discussion of Acceptance Sampling and comment on NECC’s approach to quality.

2. Why can’t every vial be tested?

Teaching Tip: Using an SPC Chart to Examine American Airlines’ Pilots “Sick Out”

Looking for a current business issue to illustrate statistical process control when you are covering Supplement 6? The Wall Street Journal (Sept.24,2012) notes how “American Airlines continued to rack up high numbers of flight delays and cancellations, blaming a dispute with its pilots union. The union, meanwhile, denied that pilots disrupted flights unnecessarily.”

Percent of Pilots Sick

Can the same set of data be used to make opposite points in an argument?  It’s not that statistics lie, it is more in how we present all of the available data points, as can see in this timely example regarding the alleged “sick out” of American Airlines pilots. Here is a 13 month “snapshot” of percent of pilots out sick at American that you can use in class:  9/18/11, 4.9% ; 10/18/11, 9.5% ; 11/18/11, 5.0% ; 12/18/11, 6.5%, ; 1/18/12, 5.4% ; 2/18/12 , 6.6% ; 3/18/12, 6.6% ; 4/18/12, 6.0% ; 5/18/12, 7.0% ; 6/18/12, 7.4%; 7/18/12, 6.1%; 8/18/12, 6.6%; and 9/18/12, 7.5%. (The number of pilots dropped a few percent during this period in American’s financial struggles, from a high of 7,840 to a current 7,563.)

“By my calculations,” writes a Dallas Morning News(Sept. 20, 2012) reporter, “the number of pilots on sick leave was 45.7% higher on Sept. 18, 2012, than on Sept. 18, 2011, up 177 pilots. That seems like an increase in sick leave usage”. (See the bar chart graph above used to make this point).  American’s spokesman adds that sick leave “has been up more than 20 percent year over year and has been elevated for months.”

13 Month SPC Chart

Counters the union: “Contrary to claims by management, we have confirmed that pilot sick rates have not deviated from historical norms”. (Here we see the SPC p-chart showing percent of sick days being within p-chart control limits).

What happens to the p-chart if the 1st two months last year are excluded? Ask your students to recompute the control limits and draw conclusions.

Video Tip: Darden Restaurant’s Quality “From Farm to Fork”

What I really like about this 12 min. video on Darden Restaurants (Olive Garden and Red Lobster) is that the VP-Quality comes right out and says “we use SPC charts, Pareto charts, process flow diagrams, fishbone charts, and scatter charts”. When you are teaching Ch. 6 and Supp. 6, it’s good for your students to hear that a real company is employing all the tools they see in the text (as in Figure 6.6).

Darden calls its quality program “From Farm to Fork”, since the inspection process begins at the food source (be it farm or pond), continues with inspections throughout the supply chain, and ends with a final check by the chef and server before the customer is served. Fifty scientists and health specialists work in QA throughout the world, most close to the food source outside the US. With 50 million pounds of seafood coming into the US for Darden each year, it is clear that quality cannot be considered just at the end of the supply chain.

The video presents real data in the form of x-bar and R-charts and capability histograms and shows what happens when specs are not met on products like steaks, salmon fillets, and chicken breasts.

Before showing the film, you may want to ask students where they think inspections are taking place on a fish that is caught in Thailand and served 48 hours later in say, Dubuque, Iowa.

Teaching Tip: Building an SPC Chart with Airline Safety Data

A very interesting article just came out in US News and World Report (Jan.25,2011) that deals with airline safety “incidence reports”. I thought the data might make a good in class example of how to build and interpret a p-chart when you teach SPC in Supp.6. Here is the scenario US News reports:

 All the major US airlines are very, very safe, to begin. Rarely do they end with a fatal crash (the last one was Feb.12, 2009 when Continental Connection #3407 killed 50 people when it crashed in Buffalo). But safety incidents do occur. (Recall the plane that landed in the Hudson River not long ago).  Using FAA and other sources, documented incidents (such as mechanical issues) for the 8 largest carriers follow.

Jet Blue: 17 incidents per 219,000 flights in 2010. This averages to a p- value of .0000776

American Airlines: 87 per 1,241,000 or p=.0000701

United Airlines: 49 per 1,204,500 or p=.0000407

Delta Airlines: 77 per 1,994,725 or p=.0000386

Continental Airlines: 23 per 884,395 or p=.0000260

US Air: 24 per 1,131,865 or p= .0000212

Southwest Air: 23 per 1,131,500 or p=.0000203

Air Tran: 5 per 255,500 or p=.0000196

Take these 8 observations and have the class create a p-chart using these timely, real-world data.  Are any of the major airlines “out-of-control”? ( I computed that the overall p-bar =.000038 (at 95% confidence). The UCL=.000042, and the LCL=.000033. Only two airlines are “in control”, but 4 are better than the LCL. I did this by computing the total sample size to be 8,062,985 with no. incidences =305).

 Thanks to Prof. Kevin Watson at Iowa State for today’s link and idea.

Video Tip: SPC at Frito-Lay

Of the 30+ videos Jay and I have produced to accompany our books, I would have to say my favorite is the one called “Frito-Lay’s Quality Controlled Potato Chips” (to accompany Supp.6, SPC). Why is it top of my list?

There are a few reasons. First, its the only video we ever made where I got to star! Normally, our films are narrated, then Jay and I come on at the end to summarize a few points. But in this one, I act as narrator. Second, this is a pretty exciting topic…watching how chips are made and seeing how critical a role SPC and TQM take.  Third, because my older son and some of his friends were given a cameo eating chips (early in the video).

But the most important reason I like to show this 10 minute video in class is because it shows the SPC process from start to finish. We see how the chips are inspected and tested at 9 checkpoints. Even better, we create, from scratch, an X-bar chart. This means setting the upper and lower control limits in a real company, for a real process that every student can relate to. So this video is a tutorial of sorts.

When I teach SPC, I stop the video at each math step along the way and recreate the numbers in the video on the board. I like to take my time and make sure the students comprehend each calculation in the video. Supp.6 takes on a more important role when the class sees that an everyday firm has to use all the tools we talk about.