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Poka Yoke

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Q 67. Give some examples of Mistake-Proofing where implementation did not meet the intended objective. What can be done to avoid such cases? 


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Would like to stick to one example of a form required to be filled online following elaborate business rules. The complexity necessitated a check of atleast the critical, sensitive fields, which if mis-filled, could cause fatal errors. Very soon, the usual pressure of targets over-ruled "old-fashioned" quality intents and staff started submitting forms without even a cursory glance at what they had hurriedly keyed in.


The Quality team dutifully created a hard copy checklist to be filled in for every form which was supposed to make the Inputter check the entry before checking the relevant item in the list. Some sanity was restored and Quality stabilized albeit temporarily. But with the characteristic vigor in beating the system which Operations usually displays, the Inputters continued their "Rajadhani" speed data entry while filling in all checklists at the end of the shift long after submitting the form and committing the erroneous information to the customer.


The Quality team then got wise to this when customer complaints resumed and stepped in with random audits at different points of time during the shift covering various combinations of transaction types, time of the day, day of the week, staff and so on. The Auditor would pick up completed transactions at random and demand the check list. If the checklist were not available, the staff could face disciplinary action. Again there was a brief lull in customer complaints, which was all too short-lived as the Inputters began to take calculated risks.


The Quality team then made the checklist too online instead of the hard copy which was supposed to ease up the job of filling the checklist, but it proved to be mere wishful thinking. Finally, technology was brought in which prevented the Inputter from submitting the form unless the check-list was filled in and submitted. This was effective but Operations still complained about reduced productivity and rising costs.


More advanced technology was introduced which used business rules to fill in all rule-driven fields and left only those fields which required thinking and judgment to be manually filled in. The Inputters were now given other fancy designations like, "Validators" or "Integrators" and were sufficiently self-motivated to do their own checks of the manually entered fields, which improved Quality.

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Example 1


In restaurants when a waiter comes to take an order with a order slip in his hand this is an example of Poka-Yoke as once the waiter writes the order for the first time he again repeats the order with them to ensure he has taken the correct order.


While incorporating this error proofing into the work environment, understanding human limits is essential. These limits include:

Hearing: Individual upper and lower thresholds of hearing change of the waiter when background noise is added.

Repetition Ability: Muscular efficiency and mental tracking decrease of the waiter as rates of repetition increase.

Therefore in the above example though mistake proofing was in place still it could not be utilized to 100% because of the environmental and physiological factors.


Example 2


Suppose a salon shop is thinking on how to increase their low client turn out. The salon is a service oriented business therefore there a lot of avenues where an error may occur. Errors or mistakes can be caused by either employees or customers. The goal of Mistake Proofing is to identify these potential errors to prevent defects from happening.

A possible error may occur as soon as the customer enters the salon. It could be a displeased customer because he or she was not immediately greeted by the staff or the staff was not there to welcome them. To address this possible error using Mistake Proofing, the salon can install an electronic sensor or hang a bell to signal the staff that someone had entered the shop. Another Mistake Proofing solution is to assign a staff whose job is to welcome the customers.


Potential errors caused by employees may happen every step of the service process. From asking what salon service the customer wanted, doing the service, asking if the customer wanted additional salon service or wants to avail their promotion, securing payment, and up to the time the customer leaves the salon. Every step should be considered and all possibilities should be studied to be able to come up with solutions that will prevent further defects.

A possible error on the part of the customer is that when they are greeted and asked what kind of salon service they wanted, they would not understand this question if there is loud noise produced either by people inside the salon or music from an audio player. A Mistake Proofing method that aims to prevent this from happening is to ensure that music inside the shop should be in minimal volume so it will not cause distraction to other people. Staff should also be trained to use audible not loud voice when conversing with their customers. Setting of rules such as no horse-play, no distractive conversations amongst staff is also an example.



Example 3


The fingerprint sensor on the iPhone is a great example of a Poka-yoke failure. Setting up a password and typing it in every time can also be tedious, and there’s also a slight chance you can forget your password. The fingerprint sensor is a great solution to this, because it’s faster than typing in a password. But the problem is that many times due to accident/age if there is a change in the muscular structure of a finger the sensor would not be able to realize the finger print and thus it causes the error


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