Bending Paper Clips to Demonstrate Natural and Assignable Cause Variation
Janice B. Eliasson and Peggy L. Hedges
Haskayne School of Business, University of Calgary, Canada
Volume 18: 2024, pp. 00-00; ABSTRACT
Statistical Process Control (SPC) is a technique that is concerned with monitoring
process stability. The authors have designed and tested a 20-minute hands-on activity that
requires participants to bend paper clips until they break. This activity has been found to assist
students in more easily understanding the difference between natural (also called normal,
common, random, or chance) and assignable (or special) cause variation in SPC. The activity,
although developed for use in a senior level Quality in Products and Services class, can easily
be used at junior level Operations Management courses that include SPC calculations. This
activity can be used prior to, or after, teaching control limits concepts.
Keywords: statistical process control; active learning; assignable or special cause variation;
natural, normal or common cause variation; out-of-control process
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