Table 2.

Types of usage metrics collected in included studies (N=49).

Characteristic		Number of studies, n (%)	References
Number of usage metrics analyzed
	1	17 (35)	[39,41,43,50,56,58-60,67,73,76,77,81,84-87]
	2	8 (16)	[42,45,47,51,54,68,69,80]
	3	10 (20)	[40,44,49,53,62,64,65,72,75,82]
	4+	14 (29)	[46,48,52,55,57,61,63,66,70,71,74,78,79,83]
Type of metrics collected (multiselect)
	Number of clicks	1(2)	[61]
	Number of features used	18 (37)	[40,41,46,48,51,52,57,62,63,65,66,68,69,71,72,74,79,83]
	Number of log-ins	20 (41)	[49,52,54-57,61-64,66,70-72,74,75,79,80,83,87]
	Number of modules	27 (55)	[43,45-47,50,53-55,57,58,60,62,64,66,67,69,70,73-76,78-82,86]
	Number of page views	10 (20)	[44,48,49,51,61,70,74,77,79,83]
	Number of posts	5 (10)	[44,63,70,71,78]
	Number of sessions	9 (18)	[39,42,46,48,52,53,55,74,78]
	Rate of return	4 (8)	[70,71,74,83]
	Session duration	24(49)	[40,42,45,46,48,49,52,53,55,57,61,64-66,68,70,74,75,78,79,82-85]
	Other (eg, calculated metrics)	14 (29)	[40,44,46,47,52,55,59,61,65,70,72,74,82]