The chocolate product M&M's is produced with the following seven-step production process, which can make over one hundred million M&M's per day.
1. Liquid chocolate is poured into molds, creating the chocolate core of the M&M's.
2. The chocolate is tumbled to make the chocolate core smooth and round. The chocolate is then given time to harden.
3. A conveyor belt transports the M&M's to the panning operation.
4. At panning, the chocolate cores are rotated and liquid candy is sprayed onto them. Multiple coatings are applied and each coating is
allowed time to dry.
5. Color is added as the final coat. Each batch has a different color and then batches are mixed across colors.
6. The "m" is then stamped onto each M&M by a special machine, avoiding any cracks in the candy shell.
7. A special packaging machine pours the proper amounts of M&M's into the bags and then seals the package. From there, bags are
combined into a carton box.
Before packaging (step 7), the quality of the individual M&M's is evaluated. Pieces are sifted to eliminate misshapen pieces. Missing
imprints, however, are not considered a reject.
A chocolate-loving operations professor has collected a sample of 120 bags of M&M's. The average weight of the bags (chocolate and bag) is
49.9783 grams. The standard deviation across the bags in the sample is 1.037 grams.
1. Assuming a lower specification limit of 47 grams and an upper specification limit of 53 grams, what is the process capability of this
process? How many defects would you expect in one million bags?
2. And, finally, which M&M product in your view has the highest standard deviation?