. Author manuscript; available in PMC: 2020 Mar 18.
Published in final edited form as: Contemp Clin Trials. 2018 Oct 2;74:55–60. doi: 10.1016/j.cct.2018.10.003
This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/BY-NC-ND/4.0/).