Index: lams_tool_assessment/web/includes/javascript/chart.js
===================================================================
diff -u -r8a1b8b9cba5668f9c9b47a716093214aeec87f30 -r98b45e9d9615cd05b9dd569e237a2bbcf2969265
--- lams_tool_assessment/web/includes/javascript/chart.js	(.../chart.js)	(revision 8a1b8b9cba5668f9c9b47a716093214aeec87f30)
+++ lams_tool_assessment/web/includes/javascript/chart.js	(.../chart.js)	(revision 98b45e9d9615cd05b9dd569e237a2bbcf2969265)
@@ -25,17 +25,20 @@
 }
 
 function drawActivityCompletionChart(data, animate){
-	var newData = [ data.possibleLearners - data.startedLearners,
-		 			data.startedLearners - data.completedLearners,
-		 			data.completedLearners
+	var newData = [ data.possibleLearners.length - data.startedLearners.length,
+		 			data.startedLearners.length - data.completedLearners.length,
+		 			data.completedLearners.length
 	   			  ];
 	if (activityCompletionChart != null) {
 		// chart already exists, just update data
 		activityCompletionChart.data.datasets[0].data = newData;
 		activityCompletionChart.update();
 		return;
 	}
-	
+
+	// store current data for custom tooltip
+	$('#activity-completion-chart').data('tooltip-input', data);
+
 	let ctx = document.getElementById('activity-completion-chart').getContext('2d');
 	
 	activityCompletionChart = new Chart(ctx, {
@@ -206,14 +209,14 @@
 							var counter = 0,
 								users = $('#answered-questions-chart').data('tooltip-input')[tooltipModel.dataPoints[0].label];
 							$(users).each(function(){
-								var portraitDiv = $(definePortrait(this[1], this[0], STYLE_SMALL, true, LAMS_URL)).css({
+								var portraitDiv = $(definePortrait(this.portraitUuid, this.id, STYLE_SMALL, true, LAMS_URL)).css({
 										'vertical-align' : 'middle'
 									}),
 									userDiv = $('<div />').append(portraitDiv).appendTo(tooltipEl).css({
 										'padding-bottom' : '5px'
 									});
 
-								$('<span />').text(this[3] ? this[3] + ' (' + this[2] + ')' : this[2]).appendTo(userDiv).css({
+								$('<span />').text(this.group ? this.group + ' (' + this.name + ')' : this.name).appendTo(userDiv).css({
 									'padding-left' : '10px'
 								});