Errors occur when our actions do not agree with our intentions even though we are capable of carrying out the task. Often, we have to act quickly in a given situation or are required to accomplish a number of tasks sequentially or even simultaneously. Making these slips is part of being human. We might do such things as:

• Forget to enter information or enter it incorrectly
• Leave out a step in a process or do them in the wrong sequence
• Include the wrong merchandise in a shipment
• Try to use something in the wrong way
• Put something together wrong

Although these errors or slips are the result of human actions, they occur because of the interaction of people with a system. Some systems are more prone to error than others. We can reduce errors by redesigning the system to make it less likely for people in the system to make errors. This type of system design or redesign is called error proofing.

The frequency of errors is a function of the number of opportunities to make errors and the probability of making an error given we have the opportunity. For example, if the same information is entered in the computer on three separate occasions, we would expect three times more errors than if the information were only entered once.

We should always be looking for ways to reduce the number of steps in a process or the number of parts in a product. This will allow for the opportunities for errors to be reduced. Error proofing is then used to reduce the probability of making an error for a given opportunity. We can error proof by using technology (e.g., adding equipment to automate repetitive tasks), by using methods to make it more difficult to do something wrong, or by the integration of these methods with technology. Methods for error proofing are not directed at changing people's behavior, but rather at changing the system to prevent slips. The methods are directed at reducing errors from actions that are done almost subconsciously when performing a process or using a product.