Table 2.

Sample size estimates by study aim

Study aim	Survey	Target population	Sample size	Assumptions
Study aim 1a*	Face to face survey to measure changes in infant feeding practices	Women 5–7 months pregnant in four districts of MP	5000	• 5% change in reported practice of immediate and exclusive breastfeeding • Loss to follow-up of 20% from enrolment to final follow-up visit • Variance inflation factor of 1.25
Study aim 1b	Phone survey to measure changes in infant feeding	Postpartum women randomized to Kilkari	5000	Descriptive survey; administered to all women enrolled into the study
Study aim 1c*	Test-retest	Women 5–7 months pregnant in four districts of MP	168 women to be interviewed twice	• Proportion of positive responses of 0.35 for rater 1 and 0.40 for rater 2 • Adjusting for a 15% loss to follow-up/refusal between the first and second surveys
Study aim 1*	Phone survey for postpartum women: infant feeding, essential newborn care, RMC during childbirth	Women 1–4 months postpartum in two districts of MP	880 women interviewed as part of face to face surveys contacted to yield 146 completed face to face and phone survey interviews	• 20% phone survey response rate • Proportion of positive responses of 0.35 for rater 1 and 0.40 for rater 2
Study aim 2*	Phone survey for pregnant women: RMC during pregnancy	Women 5–7 months pregnant in four districts of MP	880 women interviewed as part of face to face surveys contacted to yield 146 completed face to face and phone survey interviews	• 20% phone survey response rate • Proportion of positive responses of 0.35 for rater 1 and 0.40 for rater 2
Study aim 2	MCTS/RCH registration	• FLHWs • Block and district medical officers • Data entry officers	64 in-depth interviews, 24 focus group discussions, and 24 observations
Study aim 4	User perceptions of Kilkari	• FLHWs: ASHAs, ANMs • Women enrolled to Kilkari and male phone owners	49 in-depth interviews and six focus group discussions

*Sample estimates based on kappa of 0.80, alpha of 0.05, margin of error of 0.05%