. Author manuscript; available in PMC: 2018 Mar 14.
Published in final edited form as: Contemp Clin Trials. 2017 Dec 27;66:1–8. doi: 10.1016/j.cct.2017.12.016
This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/BY-NC-ND/4.0/).