Here is the design of a clinical trial:

Official Title: A Randomised Waiting-list Feasibility Study and Process Evaluation of a Psychosocial Education Programme for Young People With Type 1 Diabetes - the Youth Empowerment Skills (YES)

Included conditions:
- Diabetes Mellitus, Type 1

Study Armgroups:
- {'label': 'Intervention', 'type': 'EXPERIMENTAL', 'description': 'The intervention arm will receive the Youth Empowerment Skills (YES) programme.', 'interventionNames': ['Behavioral: Youth Empowerment Skills']}
- {'label': 'Waiting-list control', 'type': 'OTHER', 'description': 'The waiting-list control arm will receive usual care for six months before receiving the Youth Empowerment Skills (YES) programme.', 'interventionNames': ['Behavioral: Waiting-list control']}

Interventions:
- {'type': 'BEHAVIORAL', 'name': 'Youth Empowerment Skills', 'description': 'The Youth Empowerment Skills (YES) programme is a novel psychoeducational intervention with simulation-based experiential learning tailored to the needs of young people. It is based on a social-cognitive learning model, and comprises attendance at 3 all-day YES sessions in non-healthcare settings (groups of 10); and then post-programme networking through social media and follow-up events facilitated by the youth worker. Sessions are led by a peer-educator and a health professional', 'armGroupLabels': ['Intervention']}
- {'type': 'BEHAVIORAL', 'name': 'Waiting-list control', 'description': 'Usual care for 6 months, followed by the YES programme.', 'armGroupLabels': ['Waiting-list control']}

Primary Outcomes:
- {'measure': 'Glycated haemoglobin (HbA1c)', 'description': 'HbA1c will be used to measure:\n\n1. the number of participants achieving clinically significant reductions of 5.5mmol/mol or more and mean differences between groups over time\n2. the standard deviation (SD) of the mean difference between the intervention and control group in HbA1c at 6 months; for the control group the SD of the mean difference between HbA1c at 12 months and pre-exposure (phase 2) and for the phase 1 intervention group the SD of the mean HbA1c difference between post (6 and 12 months) and pre-exposure.', 'timeFrame': 'Baseline, 6 months, 12 months'}

Please estimate the sample size based on the assumption: 
The study is not statistically powered to estimate a clinical effect. An estimated 20% drop-out rate is considered.
Participants and sample size
        We aim to recruit 50 young people and randomise half to the phase 1 programme exposure, and half to the phase 2 exposure. The inclusion criteria will involve:
        
          
            Age 14â19 years.
          
          
            Diagnosis of T1DM.
          
          
            Suboptimal glycaemic control (HbA1c>69âmmol/mol or 8.5%).3
          
          
            No current or planned attendance of other structured education programmes.
          
        
        Participants will be excluded if they: have a severe physical or mental illness, unstable retinopathy, significant learning difficulties; are unable to communicate in English; or are pregnant. Participants meeting the inclusion criteria will be recruited opportunistically at the participating centres through clinical referrals and patient database searches. Based on recruitment to the pilot study, we estimate that we will be able to recruit >30% of eligible patients. To increase engagement, we will run the full study, including programme occurrences and follow-up sessions, during school holidays as this was identified by young people as the optimal period for running the YES programme.
        As a feasibility evaluation, the study is not statistically powered to estimate a clinical effect. Instead, we aim to estimate the effect-size/SD of outcomes to formulate a power calculation for a definitive trial. National Institute for Health Research guidance indicates that samples of 24â50 are adequate for this purpose.33â35 We have inflated our sample to allow for an estimated 20% drop-out rate.