Which concept is used to evaluate how effectively users can achieve their objectives?

The concept used to evaluate how effectively users can achieve their objectives is effectiveness. Effectiveness measures whether users can complete their tasks accurately and successfully within a given system or design. It focuses on the outcome of user interactions, assessing whether users can achieve their goals and how well the design facilitates this process.

In the context of interactive design, effectiveness is crucial because it directly impacts user satisfaction and the overall success of a product or interface. A design that enables users to reach their objectives with minimal hindrance is considered effective, promoting a positive user experience.

While efficiency pertains to how quickly or resourcefully a user can accomplish their goals, it does not inherently address whether the objectives are achieved successfully. Utility reflects the usability and functionality provided by a system to fulfill user needs but does not measure the success rate of those attempts. Safety relates to minimizing risk while using a product and is more focused on preventing harmful situations rather than directly measuring task accomplishment. Therefore, effectiveness stands out as the primary measure of success in achieving user objectives.