Improving Product Reliability and Software Quality, 2nd Edition

3Understanding Why Products Fail

3.1 Why Things Fail

When we talk about product reliability, we are describing the trouble‐free time period before a product fails. A failure is anytime the product does not function to specification when the product or service is needed. There are degrees of failure; for example, a color television that only displays black and white images, or a remote control that can change channels by using the number keypad, but not with the channel up and down control. A new shirt that quickly loses a button and hangs unworn in the closet constantly reminds the consumer of their dissatisfaction. These are not complete failures, but the effects they have on subsequent purchases are the same. An automobile that stops on the way to a job interview, a computer that crashes in the middle of tax preparation, or a parachute that doesn't open are much more severe failures. These failures are often communicated to others and have a more devastating effect on profit and future market share. The list is endless; the degree of failure can be varied, but the negative effect on your business is the same. A dissatisfied consumer results in the loss of repeat business.

What causes these failures? They can be due to inadequate design, improper use, poor manufacturing, improper storage, inadequate protection during shipping, insufficient test coverage, or poor maintenance, to name just a few. A product can be designed to fail, although unintentionally.

For example, a large ...