OpenClinica User Manual/Dropdowns

Advantages of a dropdown
OpenClinica can be presented in several ways, one of which is a single-select dropdown. This is a particularly useful format because:
 * It comes preset (the first item on the list or a specified default is selected). In comparison Radio buttons don't come preset (all selections are empty).
 * This preset nature allows calculations within the form to detect whether the question has been answered or not. This is useful for scored questionnaires where the number of questions answered affects the calculation.  Unset fields (e.g. radio buttons) can't be calculated in such a way.
 * It can be unset back to the first item in the list or the default. In comparison, Radio buttons can't be unset.
 * Unset items can be hidden by the actions of other fields (so the user can back out of making changes)

Adding an empty option value
Single-select dropdowns store their values in one field (RESPONSE_VALUES_OR_CALCULATIONS) and their displayed text (RESPONSE_OPTIONS_TEXT) in another. The list of values can include blank, e.g. this YESNO single-select has a '(select)' option that has a blank associated value:

By setting this field as REQUIRED, the user has to select one of the none-empty values. In this example either 'Yes' or 'No' has to be selected, (select) can't remain selected on save.

If an option that doesn't appear in the RESPONSE_VALUES_OR_CALCULATIONS list is specified as the DEFAULT, then this will appear in the single-select list. However, this method has at least one limitation due to an associated bug in version 3.1.2 of Openclinica - Issue 10611 (login required).