. Author manuscript; available in PMC: 2020 Nov 1.

Published in final edited form as: Contemp Clin Trials. 2019 Sep 13;86:105849. doi: 10.1016/j.cct.2019.105849

Table 5.

Engagement index (EI) indices and metrics

Indices	Definition	Analytic Equivalent
Click Depth Index (Ci)	The number of pages viewed in one session (session = 30 minutes) by a single internet connected device	pages/session
Loyalty Index (Li)	How many sessions per user	# of sessions per user
Interaction Index (Ii)	# of links clicked, # of interactive text, email message sent	links clicked from text/email messages
Recency Index (Ri)	How many days since last visit to the website	# of days since last session
Feedback Index (Fi)	Short website survey given at the final time point