The described issue violates the usability heuristic "User control and freedom," as defined by Jakob Nielsen.
This principle emphasizes that users should have the ability to undo and redo actions and navigate freely without being trapped in irreversible sequences. In the scenario, users are forced into the checkout process without a clear way to return or correct mistakes, except through the unreliable and disruptive back button.
This design flaw undermines user autonomy and can result in lost progress or frustration.
References:
Nielsen Norman Group: 10 Usability Heuristics for User Interface Design ISO 9241-110:2020 - Interaction Principles
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Human-centered design, as defined by ISO 9241-210, emphasizes early user involvement, iterative design, and continuous usability evaluation. Option D aligns with this model as it begins with understanding user needs (interview users), proceeds through iterative prototyping (which allows for continuous improvement), and involves user evaluation. This ensures that the final product is shaped by real user input and feedback.
Options A and B lack iteration and continuous evaluation, while option C, although partially aligned, lacks explicit user involvement in the evaluation process, focusing only on expert reviews.
References:
ISO 9241-210:2019 - Human-Centered Design
Nielsen Norman Group: Human-Centered Design Principles
Usability.gov: Human-Centered Design Process
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Usability is defined in ISO 9241-11 as the extent to which a system can be used by specified users to achieve specified goals with effectiveness, efficiency, and satisfaction in a specified context of use. Without knowing the context-such as product complexity, user familiarity, device type, or purchasing habits-it is impossible to judge whether five minutes is good or bad. For complex items, five minutes may be reasonable, while for one-click purchases, it may be excessive. Thus, usability cannot be assessed solely based on one metric like time-it must be evaluated within its full usage context.
References:
ISO 9241-11:2018 - Usability Definitions and Concepts
Nielsen Norman Group: Context of Use in Usability Testing
Usability.gov: Usability and Context of Use
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Moderating the usability test is a core activity during the actual usability test session. The moderator guides participants through tasks, ensures the session stays on track, and avoids introducing bias. Option A (testing the setup) happens before the session, during preparation. Option C (extracting findings) occurs during analysis, after the test. Option D (talking during task execution) should be minimized unless necessary, to avoid influencing user behavior. Therefore, option B is the only correct answer aligned with best practices in usability testing.
References:
Nielsen Norman Group: Role of the Usability Test Moderator
ISO 25062:2006 - Usability Test Documentation
Usability.gov: Conducting a Usability Test
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Option B represents a realistic, goal-oriented scenario that reflects how an actual user would interact with the website. It incorporates context, user intent, constraints, and desired outcome-all characteristics of well- designed usability tasks. Option A is vague and lacks real-world motivation. Option C is too prescriptive and limits insight into user behavior, while D is a survey question, not a usability task. According to Nielsen Norman Group and ISO 25062, the best usability tasks are scenario-based, realistic, and outcome-driven- making B the correct answer.
References:
Nielsen Norman Group: Writing Effective Usability Tasks
Usability.gov: Scenario-Based Usability Tasks
ISO 25062 - Usability Test Reporting
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