Imagine you are in a restaurant and ordered one of your favorite foods. Surprisingly the food was tastier than ever and you loved it so much. Next day you again ordered the food and enjoyed it in the same restaurant. The taste was almost similar. Now, you want one of your friend too taste the same as like you. So, you take him there on the third day. Unexpectedly, the taste of the food was not as expected and similar to you had already. Your taste buds senses there is a variation in the food and you are not happy. It might have happened to you in some part of life.
The point I would like to make here is, customers unknowingly expecting the same good services every time from a supplier. To be precise, customer wants nil variations in the product and services.
Jack Welch once said, while business leaders look at mean of their services, customers are looking at variations. Because variations are more visible to the customers, because it is leading to defects in the product in so many ways.
Reduce the variation in the operator handling, machine capabilities, raw material properties, environmental changes to get more accurate product consistently. We should note that, variations cannot be eliminated to zero. But the satisfaction of customers is directly proportional to variations in the product and services
In 1970s Japanese Automobile Manufacturers were far ahead of American Industries. Because of one reason. That is less variations in the Japanese products. Statistical Quality Control emerged as a branch of Quality Engineering only to reduce the variations. Because Variation is considered as Evil to Customer Satisfaction.
Design of experiments (DoE) helps the organization to develop a process that produces less variations. This acts as a Proactive tool Sampling techniques in inspections merely a reactive tool as it only segregates good from bad and not assuring the quality by sending feedback to the processes Control chart is used to reduce the process variations during manufacturing and assembly. It is less proactive and more reactive.
Understanding these tools and implementing the same helps a business to produce products and services that has less variations. This is ultimately leading to higher customer satisfaction.