Controller file in container component used in Lightning Events Tutorial Part 3 by SFDC Stop - added event.stopPropagation();

LightningEventsCompContainerController.js

({
	// Function to handle Lightning Event
	handleTotalIncomeComponentEvent : function(component, event, helper) {
		alert('Event handler at the parent component');
		// Getting the value of totalIncome attribute of event using event.getParam()
		var totalIncome = event.getParam('totalIncome');
		// Setting the totalIncome attribute of component with the event's totalIncome attribute value.
		component.set('v.totalIncome', totalIncome);
		event.stopPropagation();
	}
})