In EHQ, you can enable an option within a checkbox, radio or dropdown question type, that will appear only if the participant selects "other" from the list of predefined answers. For example, a question you might ask is: What is your preferred sport?
If the participant chooses 'Other', you can configure for another box to appear, so that you can capture that answer as well. To do this, first create a radio button question "What is your favorite sport?" and add the known options, as shown below.
To create the "other" option, turn on the Allow other options as shown below:
This will create an "Other (please specify)" option for the radio button question. The text on this option can be modified as per your requirement.
Once done you can move on to creating your next question, this will be auto saved.
NOTE - The "Allow other option" is present only for the radio, dropdown and checkbox question types on the survey.
Illustrated below is a view of how a participant would see this question on the front end when taking the survey.
If the participant selects "Other" an additional box appears for input.
As with any survey you set up in EHQ, make sure that you test the logic of the survey, ensuring that questions appear in the right order, as desired.
TIP : Please refer to this article about the reporting impacts of changing your survey/form after it is published.