function verifySurvey (form) {
	// check that user has selected a score
  	var found = false;
  	for (i=0; i<form.usefulness.length; i++) {
		if (form.usefulness[i].checked) { found = true; }
		}
	if ( !found ) { 
		alert('Please indicate whether you found this useful before submitting. The data has not been sent.');
		return false; 
		}
	
	// ask for a comment if the score was low
	var found = false;
	for (i=0; i<3; i++) {
		if (form.usefulness[i].checked && !form.comment.checked) { 
			msg = "You indicated a score of "+form.usefulness[i].value+"/5. Since this is a low score we would "
			    + "appreciate it if you would explain why in a comment.\n"
			    + "(If you assigned a low score by mistake, say 'OK' and you will be able to change your score.)\n"
			    + "Do you want to add a comment?";
			if (confirm(msg)) { form.comment.checked = true; }
			break;
			}
		}
	return true;
	}