Here is the design of a clinical trial:

Official Title: A Multi-site Randomised Controlled Trial Assessing the Effectiveness of the Little Journey App at Reducing Peri-operative Anxiety Compared to Standard Care.

Included conditions:
- Anxiety Acute
- Anxiety Fear
- Peri-operative
- Psychological Distress
- Surgery
- Children, Only

Study Armgroups:
- {'label': 'Standard Care arm', 'type': 'NO_INTERVENTION', 'description': 'Participants will receive standard of care from the pre-assessment clinic until discharge.\n\nA typical preparatory National Health Service pathway would include: meeting a specialist nurse in the preoperative assessment clinic; a preoperative anaesthetic and surgical consultation; interaction with health play specialists on the day of surgery; and distraction interventions such as hand-held tablets during induction of anaesthesia. Participants may have inhalation or intravenous induction depending on the primary management plan of the anaesthetist in charge.\n\nParticipants in the standard care arm will also receive a virtual reality cardboard headset, which can be taken home, personalised and decorated before use with virtual reality apps available to download from the app stores.'}
- {'label': 'Intervention arm', 'type': 'EXPERIMENTAL', 'description': "Participants allocated to the intervention arm will receive the same peri-operative management as the standard care arm and will also receive an access code enabling them to use the Little Journey app in the weeks leading up to their operation. We suggest the Little Journey app is used in the days to weeks leading up to the child's operation depending on their age. On downloading the app, if parents/carers insert the age of the child and date of surgery into the Little Journey app they will be sent a push notifications reminding them when to use it according to their child's age. However, it can be used as frequently as the child and/or their parents or carers wish before the operation.", 'interventionNames': ['Device: Little Journey app']}

Interventions:
- {'type': 'DEVICE', 'name': 'Little Journey app', 'description': 'The Little Journey app allows children to explore 360-degree hospital environments familiarising and desensitising them to areas and staff they\'ll see on the day of surgery. Children can "visit" the day case ward, anaesthetic and recovery rooms where their operation will occur -all while feeling safe in their own home. As the child explores the three areas, they are introduced to animated characters of staff who explain what will happen, the equipment that will be used and how they might feel. Using head tracking technology, the child triggers the animated characters by looking at them; meaning they control the pace of learning and speed at which they progress. The preparatory tool follows a pre-set story-line reflecting what happens from admission to discharge on the day of surgery.', 'armGroupLabels': ['Intervention arm']}

Primary Outcomes:
- {'measure': 'Modified Yale Pre Operative Anxiety scale - short form(m-YPAS-SF)', 'description': 'An independent and blinded observer completed observational scoring tool. Children are scored in four categories: Activity, vocalisations, emotional expressivity and state of apparent arousal, according to pre-determined Likert scale observations. Each category score is divided by its highest possible score, before being added together; these scores are then divided by four and multiplied by 100, giving a value between 22.92 to 100. Higher values indicate greater anxiety levels, with scores greater than 30 typically representing clinically significant anxiety.', 'timeFrame': 'Day of surgery (Day 1): Measured during the induction of anaesthesia in the anaesthetic room'}

Please estimate the sample size based on the assumption: 
The interim analysis used a nominal 5% significance level with an O'Brien-Fleming adjustment within a Lan-de Mets framework. The primary outcome was analyzed with a statistical stopping rule for safety only.
Interim analysis and revision of sample size estimation and trial protocol
        We planned to perform an interim analysis following the recruitment of 100 participants to the trial, to check that the baseline rates and variability in m-YPAS-SF which have guided our sample size calculations hold true in our expanded study population. Due to the pandemic, this was performed early with 119 participants recruited and 67 participants having completed their primary outcome data collection. The primary outcome was analysed with a statistical stopping rule for safety only. This analysis was carried out using a nominal 5% significance level with an OâBrien-Fleming adjustment (within a Lan-de Mets framework). This identified no evidence of harm or need to stop the trial.
        However, this analysis revealed a poor correlation between the baseline and preanaesthesia m-YPAS scores. Consequently, the sample size was recalculated without the baseline adjustment, resulting in a revised sample size of 596 patients. The baseline, prerandomisation mY-PAS-SF score was also dropped from data collection.