Require responses for opinion pre-survey and opinion post-survey

[JamesPHoughton]

As experiment designers, we want to require that participants complete the pre/post opinion surveys, so that we don't have to account for missing data in our statistical analysis.

At the moment, we haven't built up the capability to make these questions required. We have a dev issue open here:

• [ ] https://github.com/Watts-Lab/deliberation-empirica/issues/458

When the code is in place to allow this, we will need to:

• [ ] update the treatment file with the syntax for making things required
• [ ] test that we have implemented everything correctly
• [ ] update our design document to state that the questions will be mandatory

[xehu]

+1!!