In order to bind the chart each series as well as the x-axis labels should refer to the corresponding field from the data source. In your case you need two fields - one with responses for the x-axis and the other with average for the bar series.
You can examine the data binding demos
for more information on the matter.
On a side note - the chart can only be bound to a single data source. You may also find useful this code library regarding manual data source grouping - http://www.telerik.com/support/code-library/group-radhtmlchart-data-source