Poka yokes are procedures that block the inevitable mistake from becoming a service defect

1. We believe that fail-safing has decided advantages over the other logical choice for service process control, statistical process control (SPC). This is due to the humanistic nature of services, which makes them particularly prone to human error. As a statistical method, SPC is designed to ignore random variation and signal statistically significant events. Human error is, however, a random event and thus will be ignored by SPC. (In SPC terminology, human error will become part of the common cause variation.) Therefore, if SPC cannot detect human error, then it will not be able to control its effect on the service process.

2. R. Hall, Attaining Manufacturing Excellence (Homewood, Illinois: Dow Jones-Irwin, 1987).

3. S. Shingo, Zero Quality Control: Source Inspection and the Poka-yoke System, trans. A.P. Dillon (Cambridge Massachusetts: Productivity Press, 1986).

4. A.G. Robinson and D.M. Schroeder, “The Limited Role of Statistical Quality Control in a Zero Defect Environment,” Production and Inventory Management Journal 31 (1990): 60–65.

5. T. Levitt, “Production-line Approach to Service,” Harvard Business Review, September-October 1972, pp. 41–52. Levitt reveals how, to keep its surrounding property clean, McDonald’s placed numerous conspicuously colored trash cans throughout the parking lots. The assumption was that customers would not litter while looking at an obvious trash can only steps away.

6. A. Parasuraman, B. Zeithaml, and L. Berry, “SERVQUAL: A Multiple-Item Scale for Measuring Customer Perceptions of Service Quality,” Journal of Retailing, Spring 1988, pp. 12–40.

7. SERVQUAL is primarily a measurement tool, and, although its dimensions represent important aspects of the service in the eyes of the customer, they do not directly relate to the activities of the server. This is because the SERVQUAL dimensions were obtained by disaggregating a perceptual construct, service quality, into factors that best explained different perceived levels of quality, rather than by grouping the fundamental observed components of the service delivery system into larger more homogenous categories.

8. K. Anderson and R. Zemke, Delivering Knock Your Socks Off Services (New York: AMACOM, 1991).

9. C. Sewell and P.B. Brown, Customers for Life (New York: Doubleday, 1990).

10. F. Luthans and T. Davis, “Applying Behavioral Management Techniques in Service Organizations,” Service Management Effectiveness, ed. D. Bowen et al. (San Francisco: Jossey-Bass, 1990), pp. 177–209.

11. R.E. Yates, “Lawyers not Exempt from Quality Crusade,” Recrafting America (Chicago: Chicago Tribune Company, 1991).

12. J. Edelson, “The Food Service Industry: Examples in Products and Services” (Los Angeles: University of Southern California, Failsafe Project Report, June 1989).

13. Andersen and Zemke (1991).

14. R. Caplan, Why There Are No Locks on the Bathroom Doors in Hotel Louis XIV and Other Object Lessons (New York: McGraw-Hill, 1984).

15. J. Kingman-Brundage, “The ABCs of Service System Blueprinting,” Designing a Winning Service Strategy, ed. M.J. Bitner and L.A. Crosby (Chicago: American Marketing Association, 1989).

16. Sewell and Brown (1990).

17. Nikkan Kogyo Shimbun/Factory Magazine, ed., Poka-Yoke: Improving Product Quality by Preventing Defects (Cambridge, Massachusetts: Productivity Press, 1988), p. 100.

18. Sewell and Brown (1990).

19. Ibid.

20. Services could benefit from a compendium of poka-yoke examples similar to those compiled for manufacturing in:

Nikkan Kogyo Shimbun/Factory Magazine (1988).

Quality Glossary Definition: Mistake proofing

Also called: poka-yoke, fail-safing

Mistake proofing, or its Japanese equivalent poka-yoke (pronounced PO-ka yo-KAY), is the use of any automatic device or method that either makes it impossible for an error to occur or makes the error immediately obvious once it has occurred. It is a common process analysis tool.

When to Use Mistake Proofing

• When a process step has been identified where human error can cause mistakes or defects to occur, especially in processes that rely on the worker’s attention, skill, or experience
• In a service process, where the customer can make an error which affects the output
• At a hand-off step in a process, when output (or for service processes, the customer) is transferred to another worker
• When a minor error early in the process causes major problems later in the process
• When the consequences of an error are expensive or dangerous

Mistake Proofing Procedure

1. Obtain or create a flowchart of the process. Review each step, thinking about where and when human errors are likely to occur.
2. For each potential error, work back through the process to find its source.
3. For each error, think of potential ways to make it impossible for the error to occur. Consider:
   • Elimination: eliminating the step that causes the error.
   • Replacement: replacing the step with an error-proof one.
   • Facilitation: making the correct action far easier than the error.
4. If you cannot make it impossible for the error to occur, think of ways to detect the error and minimize its effects. Consider inspection methods, setting functions, and regulatory functions expanded on below.
5. Choose the best mistake-proofing method or device for each error. Test it, then implement it. Three kinds of inspection methods provide rapid feedback:
   • Successive inspection is done at the next step of the process by the next worker.
   • Self-inspection means workers check their own work immediately after doing it.
   • Source inspection checks, before the process step takes place, that conditions are correct. Often it’s automatic and keeps the process from proceeding until conditions are right.

Setting and Regulatory Functions

Setting functions are the methods by which a process parameter or product attribute is inspected for errors:

• The contact or physical method checks a physical characteristic such as diameter or temperature, often using a sensor.
• The motion-step or sequencing method checks the process sequence to make sure steps are done in order.
• The fixed-value or grouping and counting method counts repetitions or parts, or it weighs an item to ensure completeness.
• A fourth setting function is sometimes added, information enhancement, which makes sure information is available and perceivable when and where required.

Regulatory functions are signals that alert the workers that an error has occurred:

• Warning functions are bells, buzzers, lights, and other sensory signals. Consider using color-coding, shapes, symbols, and distinctive sounds.
• Control functions prevent the process from proceeding until the error is corrected (if the error has already taken place) or conditions are correct (if the inspection was a source inspection and the error has not yet occurred).

Mistake Proofing Example

The Parisian Experience restaurant wished to ensure high service quality through mistake proofing. They reviewed the deployment chart (a detailed flowchart that shows who performs each step) of the seating process shown below and identified human errors on the part of restaurant staff or customers that could cause service problems.

Mistake Proofing: Restaurant’s deployment chart

The first potential error occurs when customers enter. The maitre d’ might not notice a customer is waiting if the maitre d’ is escorting other customers to their table, checking on table status, or conferring with kitchen staff.

The mistake proofing device is an electronic sensor on the entrance door. The sensor sends a signal to a vibrating pager on the maitre d’s belt to ensure that the maitre d’ always knows when someone enters or leaves the restaurant. Other mistake proofing methods replaced the process steps requiring the maitre d’ to leave the front door to seat customers.

A possible error on the customers’ part was identified at the step when diners are called from the lounge when their table is ready. They might miss the call if the lounge is noisy, if they are engrossed in conversation, or if they are hard of hearing.

The mistake proofing chosen by the team was to replace the step of the process in which the maitre d’ called the customer’s name over the loudspeaker. Instead, during the greeting step, the maitre d’ notes a unique visual identifier of one or more members of the party. When the table is ready, the table busser notifies the waiter, who comes to the maitre d’ and learns how to identify the customers. The waiter finds the customers in the lounge, escorts them to their table, gives them menus, and takes additional drink orders.

Not only does this mistake proofing method eliminate a customer-caused problem, it improves the restaurant ambiance by eliminating the annoying loudspeaker, keeps the maitre d’ at the front door to greet customers, creates a sense of exceptional service when the waiter “magically” knows the customers, and eliminates additional waiting time at the hand-off between maitre d’ and waiter.

Adapted from The Quality Toolbox, Second Edition, ASQ Quality Press.

Are procedures that prevent a mistake from becoming service defect?

Which of the following is one of the three T's used to classify poka

Which of the following refers to the physical presence of the customer in a service system?

What are the psychological benefits that the customer may sense only vaguely called?