Impact of the Umoyo mother-infant pair model on HIV-positive mothers’ social support, perceived stigma and 12-month retention of their HIV-exposed infants in PMTCT care: evidence from a cluster randomized controlled trial in Zambia

Table 2 Sample size calculation for primary outcome

α (alpha)	0.05
β (power)	0.80
π_o (average change in control facilities)	0.01
π₁ (average change in intervention facilities)	0.13
m (mean number of eligible MIPs per facility)	30
ρ (rho)^a	0.15
C (total facilities included per arm)	14

ISSN: 1745-6215