Table 1.

Feasibility outcomes and indicators.

Outcome	Definition	Indicator	Minimum required sample size
Participation completion	Number of participants who successfully complete the final questionnaire within 1 year of trial start	80% out of total randomized participants in each group	100 participants per group is needed to achieve a margin of error of 8% with a 95% confidence level
Eligibility	Proportion of participants who sign up that meet eligibility criteria	At least 50% of responses to baseline and screening questionnaires are eligible	200 participants in total to achieve a margin of error of 7% with a 95% CI
Recruitment	Number of eligible participants recruited and consented	At least 50% of target sample size of 200 randomized within 6 months	200 participants in total to achieve a margin of error of 7% with a 95% CI
Retention	Proportion of withdrawal and dropouts after recruitment	Less than 20% of the participants lost to 6-month follow-up	200 participants in total to achieve a margin of error of 5.5% with a 95% CI
Outcome acceptability	Follow-up questionnaire completion rates	70% of the questionnaires that are submitted within 7 days of notification reminder	200 participants in total to achieve a margin of error of 6.3% with a 95% CI
Intervention acceptability	Frequency of app usage in the intervention group	Answers to frequency of use and features used questions in follow-up questionnaires	N/Aa
Appropriateness of data collection processes	Completeness of data	50% of the questionnaires completed and less than 20% of the missing response rates in each questionnaire	N/A

^aN/A: not applicable.