Whether to show the back button on a survey page.
<survey> <surveypage>
A value of 1 indicates the button will be shown, 0 indicates it will not.
The following displays the value of showbackbutton in a text stimulus:
<text sometext>
/ items= ("showbackbutton = <% surveypage.page3.showbackbutton %>")
</text>
The following displays the value of showbackbutton in an instruction page:
<page somepage>
showbackbutton = <% survey.mysurvey.showbackbutton %>
</page>