Here is the design of a clinical trial:

Official Title: Adjunct Virtual Reality Pain Management in Acute Brain Injury

Included conditions:
- Traumatic Brain Injury
- Headaches Posttraumatic
- Trauma
- Pain, Acute

Study Armgroups:
- {'label': 'All patients', 'type': 'EXPERIMENTAL', 'description': 'All patients were intended to engage in three different 20-30 min sessions run by research coordinators and spaced a minimum of 4 hours apart to allow for washout of effects, including 1) a commercially available, immersive VR environment, theBlu (WEVR, Inc, Venice, California, USA) delivered via Oculus Rift (Oculus VR, Irvine, California, USA) headset (VR Blu), 2) a non-immersive two-dimensional mimic delivered via a tablet computer (Tablet Blu), and 3) a VR control session delivered via a content-less Oculus Rift headset (VR Blank). The three sessions were run by research coordinators and spaced a minimum of 4 hours apart. The intervention order was counterbalanced using a randomized sequence generator.', 'interventionNames': ['Behavioral: Virtual Reality Session (VR Blu)', 'Behavioral: Tablet-based Session (Tablet Blu)', 'Behavioral: Use of Virtual Reality Head Mounted Display without Content (VR Blank)']}

Interventions:
- {'type': 'BEHAVIORAL', 'name': 'Virtual Reality Session (VR Blu)', 'description': '20-30 minute session of virtual reality immersive content.', 'armGroupLabels': ['All patients']}
- {'type': 'BEHAVIORAL', 'name': 'Tablet-based Session (Tablet Blu)', 'description': '20-30 minute session of tablet-based content that mimics the content from virtual reality sessions.', 'armGroupLabels': ['All patients']}
- {'type': 'BEHAVIORAL', 'name': 'Use of Virtual Reality Head Mounted Display without Content (VR Blank)', 'description': '20-30 minutes session using head mounted display to reduce light and sound.', 'armGroupLabels': ['All patients']}

Primary Outcomes:
- {'measure': 'Change in Pain Score', 'description': 'Pre- vs. Post-Intervention Ratings on Numeric Pain Rating Scale. Numeric Pain Rating scale range is from 0 (no pain) -10 (severe pain)', 'timeFrame': 'Pre- and Post-Intervention (approximately 30 minutes)'}

Please estimate the sample size based on the assumption: 
30% dropout rate, 80% power, one-sided 0.05 significance level
Sample size calculation
        Prior work suggests that a 33% pain intensity difference or a 2-point difference on a 0â10 pain numeric rating scale is an appropriate surrogate for a patient-determined clinically important response.42 We will enrol 60 patients, projecting a study dropout of 30%, leaving us with 42 patients to give us an 80% likelihood to detect a treatment difference at a one-sided o.05 significance level.43 44