When possible, use a method that is equally simple and efficient for beginners and experts. Otherwise, provide methods specialized for beginners and experts. Conceal expert methods to the extent possible to minimize complexity for beginners. When systems are complex and frequently used, consider designs that can be customized to conform to

The use of more elements than necessary to maintain the performance of a system in the event of failure of one or more of the elements.

The garbage in–garbage out principle is based on the observation that good inputs generally result in good outputs, and bad inputs, barring design intervention, generally result in bad outputs. The rule has been generalized over time to apply to all systems, and is commonly invoked in domains such as business, education, nutrition, and engineering,

is often preferable to settle for a satisfactory solution, rather than pursue an optimal solution.1

The 80/20 rule asserts that approximately 80 percent of the effects generated by any large system are caused by 20 percent of the variables in that system.

Consider design by committee when quality, error mitigation, and stakeholder acceptance are primary factors. Consider design by dictator when an aggressive timeline is the primary factor. Favor

For example, new design features or elements that excite designers are often never used or even noticed by people who interact with the design. In many cases, such features and elements increase the design’s interaction costs by adding complexity to the system.

Keep the exposures brief, and separate them with periods of delay. The exposure effect will be strongest for the first ten exposures; therefore, focus resources on early presentations for maximum benefit.

The act of measuring certain sensitive variables in a system can alter them, and confound the accuracy of the measurement.