bug fix: clustering was being done on the wrong data

Change-Id: I75730de6ed8e2b0ca1b020029cc2629482500dd7
Reviewed-on: https://gerrit.instructure.com/45792
Reviewed-by: Addison Higham <ahigham@instructure.com>
Product-Review: Michael Ziwisky <mziwisky@instructure.com>
QA-Review: Michael Ziwisky <mziwisky@instructure.com>
Tested-by: Michael Ziwisky <mziwisky@instructure.com>