Here is the design of a clinical trial:

Official Title: A Randomized Controlled Group Intervention Trial for Siblings and Parents of Children With Chronic Illness (SIBS-RCT)

Included conditions:
- Siblings of Children With Chronic Illness

Study Armgroups:
- {'label': 'SIBS intervention', 'type': 'ACTIVE_COMPARATOR', 'description': 'SIBS intervention is a 5-session group intervention for siblings and parents of children with chronic illness. Sessions 1-3 are delivered in one day, and sessions 4-5 are delivered in one day one week later.', 'interventionNames': ['Behavioral: SIBS intervention']}
- {'label': 'Waitlist', 'type': 'NO_INTERVENTION', 'description': 'Waitlist is 12 week of no intervention/usual care'}

Interventions:
- {'type': 'BEHAVIORAL', 'name': 'SIBS intervention', 'description': 'SIBS is a manual-based group intervention for siblings and parents of children with chronic illness', 'armGroupLabels': ['SIBS intervention']}

Primary Outcomes:
- {'measure': 'Strengths and difficulties questionnaire (SDQ)', 'description': 'Sibling mental health, reported by siblings, parents, and main teacher', 'timeFrame': 'Pre to 12-months follow-up'}

Please estimate the sample size based on the assumption: 
Statistical power of 0.8, significance level of 0.05, intra-cluster correlation coefficient (ICC) of 0.11, inflation factor (IF) of 1.55, and a dropout/concomitant care rate of 27%
Sample size {14}
        The planned sample is 288 siblings, 288 mothers, and 288 fathers. Based on a power analysis of change in the main outcome variable (SDQ) from our open trial, with a minimal relevant standardized effect size of 0.4, a statistical power of .8, and a significance level of .05 [24], we need a sample of 136 families. The intra-cluster correlation coefficient (ICC) in our open trial was 0.11. We have taken this lack of independence between observations into account in sample size estimates. The planned group size is 6, which results in an inflation factor (IF) of 1.55 (IFâ=â1â+â(mâââ1)âÃâICC) [25]. Adjusting with this IF resulted in a sample size of 211 (IFâÃâ136). We further increased the sample to 288 to compensate for dropouts and concomitant care (estimated to 27% based on our open trial). An estimated 5000 children with ND aged 0â18âyears receive health services in the catchment area, of whom an estimated 1000 (20%) have at least one sibling aged 8â16âyears. Thus, a 29% response rate is required to reach our sample size. We believe this is a realistic goal given the response rate in our open trial was 58%, and whereas one site recruited 107 participants in our open trial, we now have eight sites.