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Table 4 Sample size estimation

From: Study protocol for a randomized, controlled, superiority trial comparing the clinical and cost- effectiveness of integrated online mental health assessment-referral-care in pregnancy to usual prenatal care on prenatal and postnatal mental health and infant health and development: the Integrated Maternal Psychosocial Assessment to Care Trial (IMPACT)

N = 2(0.84 + 1.96)2 * (σ/§)2

σ = standard deviation of the primary outcome (Depression, Anxiety, Stress subscales of DASS21)

§ = minimal clinically important difference

Depression subscale

Anxiety subscale

Stress subscale

N = 2(0.84 + 1.96)2 * (σ/§)2

N = 2(0.84 + 1.96)2 * (σ/§)2

N = 2(0.84 + 1.96)2 * (σ/§)2

N = 2(0.84 + 1.96)2 * (5.4/4)2

N = 2(0.84 + 1.96)2 *(10.2/4)2

N = 2(0.84 + 1.96)2 * (8.6/4)2

N = 28.6 per group

N = 102 per groupa

N = 72.5 per group

  1. aLargest sample size per group = 102. Total sample of women with mild to moderate psychological distress = 204. Based on a prevalence rate of 25% of low-moderate symptoms in pregnant women, a final sample size of 816 (408 per group) will be required (204/N = 25/100).
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ISSN: 1745-6215