Table 2.

Proportion of apps implementing principles of one of the four persuasive system design categories.

	Number of implemented principles
	0	1	2	3	4	5
System credibility (%)	1.7	56.7	22.5	16.7	2.5	–
Dialogue support (%)	11.7	55.0	17.5	11.7	4.2	–
Primary task support (%)	59.2	16.7	13.3	5	4.2	1.7
Social support (%)	81.7	12.5	3.3	1.7	0.8	–

Numbers represent how many apps implemented which amount of the seven principles of each persuasive system design category.