# Enhancing User Experience with Visual Controls for Local Differential Privacy
## 6 User Study
### Methodology and Setup  
Although our interface design emphasizes accessibility, we conducted a usability study that revealed that while the overall interaction was intuitive, certain components, such as the transformation table and slider explanations, require simplification or repositioning. This study seeks to confirm that abstract privacy settings can be made tangible and intuitive through visual feedback and command transformation examples.  
To evaluate the usability and interpretability of our privacy control interface, we conducted a structured user study with six participants from diverse technical and professional backgrounds (Master's in statistics and data science, 10+ years as cybersecurity and sales product manager in South America, electronics and communication engineer with 2.5 years in SAP, Bachelor's and Master's in psychology and education psychology working in educational consulting), male and female, of different ethnicities. Users had basic experience using smart home devices (e.g., Alexa and Google Home) recruited through convenience sampling (students, colleagues, and early adopters).  
Figure 5: Desktop widget with 4-level control.  
Our test setup includes _prototype_ (the interactive interface developed in Figma, with desktop and mobile views), _tasks_ (four core usability tasks performed in a 10-15 min think-aloud session), _interview questions_, and _tools_ (task sheet, observation notes, and optional recording with consent).  
**Task Scenarios.** Each participant completed a series of think-aloud tasks using our interactive prototype (see Figure 5). During this 10-15 min session, we asked participants to think out loud as they use the interface explaining what they are looking at, what they are trying to do, and what is going through their mind, especially if something is confusing.  
1. _Adjust Privacy Level_: Interact with the four-level control (Minimal, Basic, Balanced, and Enhanced). 1. Task: Change the privacy level from Minimal to Enhanced. 2. Success criteria: User adjusts slider without help. 3. _Interpret Privacy Graph_: Explain the privacy vs. personalization trade-off curve. 4. Task: Describe what the graph shows. 5. Success criteria: User recognizes trade-off between privacy and personalization. 6. _Understand Data Transformations_: Interpret how commands like \"music\" change to \"heat\". 7. Task: Explain what is happening in the before/after command table. 8. Success criteria: User identifies that commands are modified to protect privacy. 9. _Choose a Privacy Setting_: Pick a level and justify the choice. 1. Task: Select a level and explain their choice. 2. Success criteria: User justifies selection using privacy-utility reasoning.  
**Interview Questions.** After the task completion, we performed a semi-structured interview by asking the following questions:  
1. Can you describe what you think this interface is meant to help you do?
2. What did you find easy or difficult to understand in this interface?
3. How would you describe your sense of control over your data while using the interface?
4. Have you used privacy settings on smart home devices before? If so, how does this interface compare?
5. If you were designing this for others to use, what would you change or improve?