Process Variation and Quality Control!
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by michael hughes Sugar! Color! Process variation and quality control! Brock University students take a bite out of candy in bid for statistical learning You want the candy? more about the assignment, comparing notes more than in You can have the candy by taking Michael Armstrong’s other years. undergraduate quality management course at Brock Univer- “Anecdotally, they do seem more interested,” Armstrong sity in St. Catharines, Ontario, Canada. said. Rather than making up numbers, Armstrong picked six The class grouped 36 packages of each candy into subsets of popular North American candies and had his class gather data six packs per production date. Armstrong chose Mike & Ike, needed for process and quality improvement. As opposed to M&Ms, Skittles, Gobstoppers, Reese’s Pieces and Smarties. jet turbines, candy was relatively simple. Getting hard numbers on taste, certainly a customer’s No. 1 “While they’re using one side of the brain to do their heavy candy concern, would be difficult. So Armstrong had students duty statistical analysis, the other side of their brain is, hope- analyze weight and color distribution. fully, having some fun thinking about sugar, color, candy,” Weight lets consumers know whether they’re getting their said Armstrong, associate professor in the Department of money’s worth — or, in some cases, more. Color sometimes, Finance, Operations and Information Systems. but not always, corresponds to a candy’s taste. The students analyzed variance and regression, using the tools taught in class. Does the number of yellow candies Weighty subjects and tasty colors vary daily? Is there a linear trend of increasing or decreasing Armstrong picked weight to see if companies were meeting green candies per package? their legal requirement to match their contents with the box “I’ve got the assignment set up so that they’re using label. He wasn’t surprised that weight varied from box to the tools in the same order they would use them in a real box and that five of the six manufacturers overfilled to make business process in a real factory if they’re actually doing up for potential shortages. a quality improvement project, if they’re actually working, “So if you’re buying a two-ounce package of Skittles, for example, on a Six Sigma process improvement team,” you’re actually getting about 2.1 ounces, or 1.9 percent extra,” Armstrong said. Armstrong said. Armstrong hasn’t seen the feedback evaluations for the However, the amount of overfill and variation was a recent semester, the second time he has used this particular shock. For example, Gobstoppers had 10 or 11 times more candy-in-the-classroom idea. But he hears students talk variation than Mike & Ike. “I mean, we’re talking about little pieces of sugar, basi- cally,” Armstrong said. “That was kind of unexpected for me to see such a wide difference in a simple product that you would kind of think of as being almost standardized.” Gobstoppers, which had the highest standard deviation, included one box that weighed 20 percent more than the label The top row of candy is from a pack of Mike & Ike that contained lots of yellow (lemon flavor), while the bottom row shows the contents from a package that was missing yellow, but had lots of green (lime flavor). 42 Industrial Engineer Photos by Eric Jacksch weight. Another was 8 percent less than the label weight. On the other hand, the Mike & Ike jelly bean candy had almost no variation: less than one-tenth of Gobstoppers and less than a quarter of the M&Ms’ variation. But Mike & Ike had less overfill, meaning less “free candy” for customers, but less cost to the manufacturer. Armstrong also marveled at the day-to-day drift among three candies: Reece’s Pieces, Gobstoppers and Smarties. For example, Gobstoppers packages produced on Oct. 10, 2008, had about 12 percent more candy than those filled Smarties package contents are Jan. 15, 2009. arranged to form a question mark. This version of Smarties, That tells Armstrong and his students that something in similar to M&Ms, is sold only the filling process goes awry, or a machine gradually comes in Canada. out of adjustment or needs to get reset more often. Armstrong was interested in color because he’s not sure Putting a dollar amount on that is difficult, but it shows that companies think a lot about it, particularly in candies where the company’s quality doesn’t match what consumers that have the same flavor regardless of color. And while Mike might like, Armstrong observed. & Ike won kudos for consistent weight, the candy maker had Weight is a different matter. Armstrong understood why less success in the color department. Color distribution for companies with statistically significant variations compen- Mike & Ike and Smarties varied daily. sate by adding more candy to the process. Skittles, on the other hand, always had all five colors, and “That’s I’m sure much cheaper than spending however the variation was reasonable, according to Armstrong. But many millions of dollars on a new machine,” he admitted. whatever the Mike & Ike factory does for weight, it doesn’t But that overfill could have been sold for cash money. do for color. Armstrong said Mars produces 200 million pieces of Skittles “We actually got one package of our 36 that was missing per day. Average overfills of 1.9 percent, or 3.8 million pieces, yellow, which means for Mike & Ike you’re missing lemon mean that Mars effectively gives away about 3.5 tons per day. flavor, because color corresponds to flavor,” Armstrong said. “What I hope my students would say is well, gee, rather That batch averaged 3.2 yellow candies per pack. Another than buying that new machine, why don’t we put together batch, which overflowed with lemon flavor to the tune of a little process improvement team, do some Six Sigma, do 11.2 yellows per pack, contained very few lime candies. some lean, do whatever particular brand you like for your “So there’s something going on different in that Mike quality improvement,” Armstrong said. & Ike factory. It’d be really cool to poke around and go in,” Maybe Mars could cut that variation in half or by one- Armstrong said. third. That way, the company saves money without spending tons of capital money on new equipment. Factory specifications “I would like my students to graduate and actually be able No law mandates five red candies per Mike & Ike package, to go out into a small business and actually be able to do but variations could affect how consumers view the product. something like this,” Armstrong said. “They could add value “That little 12-year-old who really likes the yellow didn’t to their employer.” get any lemon flavor this week,” Armstrong said. “Well, he’s Find out more details about this “sweet” project at not going to be happy.” www.iienet.org/magazine/jan10/candy. d January 2010 43.