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Today's automation industry quiz question comes from the ISA Certified Automation Professional certification program. ISA CAP certification provides a non-biased, third-party, objective assessment and confirmation of an automation professional's skills. The CAP exam is focused on direction, definition, design, development/application, deployment, documentation, and support of systems, software, and equipment used in control systems, manufacturing information systems, systems integration, and operational consulting. Click this link for information about the CAP program. This question is from the CAP study guide, Performance Domain IV, Development.

When developing HMI screens, it is recommended that the quantity of items an operator has to remember is less than:

a) one
b) three
c) seven
d) 20
e) none of the above

Studies show people can remember approximately seven new things for about 20 seconds. This is called short-term memory. After 20 seconds, people will have lost the information if they cannot quickly store it in long-term memory.

Reference: Weinschenk, et al. GUI Design Essentials, Wiley Computer Publishing.

The best answer is C, seven.