If you want to restrict access to other apps on the iPad, and do not have a kiosk enclosure that covers the Home and Sleep/Wake buttons, you can disable them.
How to Disable the Home and Sleep/Wake Buttons
1. Launch the Settings app.
2. Tap Accessibility.
3. Scroll down and tap Guided Access.
4. Enable Guided Access.
5. Tap Passcode, and set a passcode for the Guided Access settings.
6. Return to QuickTapSurvey and launch your survey.
7. On the first screen of the survey, quickly press the Home Button 3 times.
8. Tap the Options button under Hardware Buttons if you'd like to Unable or Disable Sleep/Wake Button and Volume Buttons.(The default option is disabled)
9. Press the Start button at the top right of the screen to fully enable Guided Access.
Your Home Button, Sleep/Wake Button, and Volume Buttons are now disabled.