Controlling quality and variability

Think about your imaginary fast-food restaurant and how your customers might

describe the quality. Here are a few things that customers probably value in your

French fries:

» Ingredients that are clean and safe to eat

» Food that is fully cooked

» Consistent portion sizes (neither too big nor too small)

» Reliable availability (prepared quickly and served hot)

To meet your customers’ needs, you need to deliver high quality French fries every

time someone places an order. Customers might forgive cold fries once or twice,

but if they keep getting poor-quality products from you, they’re going to stop

coming to your restaurant.

You can measure the quality of a product  — and how much variability you

have in a process to make a product — through quality control (QC) and quality

assurance (QA).

Quality control involves testing and measuring the outputs to make sure they’re

acceptable. QC might involve pulling a few products off of the line every hour and

taking them to the laboratory for testing, or you might test-drive every new car to

make sure that it works properly.

Quality assurance is about looking at each step in a production process and ensur-

ing that things are working properly by measuring variability. QA starts with the

realization that products are the output of a process. If the process is exactly the

same all the time, the products will always be exactly the same. If a production

process changes it creates differences in the finished products.