Whether a response is mandatory for a survey item.
<caption> <checkboxes> <dropdown> <image> <listbox> <radiobuttons> <slider> <textbox>
A value of 1 indicates a response must be given, 0 indicates a response is optional.
The following displays the value of required in a text stimulus:
<text sometext>
/ items= ("required = <% textbox.q1.required %>")
</text>
The following displays the value of required in an instruction page:
<page somepage>
required = <% checkboxes.q2.required %>
</page>