Here is the design of a clinical trial:

Official Title: Photobiomodulation Therapy and Transcutaneous Electrical Nerve Stimulation on Chronic Neck Pain Patients

Included conditions:
- Chronic Neck Pain

Study Armgroups:
- {'label': 'PBM + TENS', 'type': 'ACTIVE_COMPARATOR', 'description': 'The patients will be submitted to the active PBM and active TENS', 'interventionNames': ['Device: Active PBM', 'Device: Active TENS']}
- {'label': 'PBM', 'type': 'ACTIVE_COMPARATOR', 'description': 'The patients will be submitted to the active PBMT and placebo TENS', 'interventionNames': ['Device: Active PBM', 'Device: Placebo TENS']}
- {'label': 'TENS', 'type': 'ACTIVE_COMPARATOR', 'description': 'The patients will be submitted to the placebo PBMT and active TENS', 'interventionNames': ['Device: Active TENS', 'Device: Placebo PBM']}
- {'label': 'Placebo', 'type': 'PLACEBO_COMPARATOR', 'description': 'The patients will be submitted to the placebo PBMT and placebo TENS.', 'interventionNames': ['Device: Placebo PBM', 'Device: Placebo TENS']}

Interventions:
- {'type': 'DEVICE', 'name': 'Active PBM', 'description': 'To active photobiomodulation therapy (PBMT) the patient will be oriented to lie preferably in prone. The treatment area will be defined according to painful area. In the active group will be used the followings parameters: low-level laser therapy, 808 nm, 4 infrared diodes, 180 mW, 9 J. In the placebo PBMT will be performed a simulation of laser application. The cluster probe will be positioned on painful area during the same time of active PBMT, the equipment will be turned on and set, however the trigger will be not actived and no beam will be applied.', 'armGroupLabels': ['PBM', 'PBM + TENS']}
- {'type': 'DEVICE', 'name': 'Active TENS', 'description': 'To active transcutaneous electrical nerve stimulation (TENS) the patient will be oriented to lie preferably in prone. Two or four electrodes standard square self-adhesive electrodes (5 × 5 cm2) will be positioned according to the painful area related by patient. It will be used the following parameters: frequency of 100 Hz, pulse duration of 125 µs (positive phase), 30 minutes of current stimulation and the pulse amplitude will be increased until the patient reports a strong but comfortable paresthesia (including motor level stimulation but no painful TENS). The amplitude will be adjusted (if necessary) each 5 minutes to keep a strong but comfortable paresthesia.', 'armGroupLabels': ['PBM + TENS', 'TENS']}
- {'type': 'DEVICE', 'name': 'Placebo PBM', 'description': 'In the placebo PBMT will be performed a simulation of laser application. The cluster probe will be positioned on painful area during the same time of active PBMT, the equipment will be turned on and set, however the trigger will be not actived and no beam will be applied.', 'armGroupLabels': ['Placebo', 'TENS']}
- {'type': 'DEVICE', 'name': 'Placebo TENS', 'description': 'To placebo transcutaneous electrical nerve stimulation (TENS) Two or four electrodes standard square self-adhesive electrodes (5 × 5 cm2) will be positioned according to the painful area related by patient. This device was customized to deliver a current for 30 seconds (both channels) and then ramp off over the next 15 seconds so that it will be active for a total of 45 seconds. This will permit the patient to fell the TENS sensation while applying the settings.', 'armGroupLabels': ['PBM', 'Placebo']}

Primary Outcomes:
- {'measure': 'Pain intensity: Numerical Rating Scale (Pain NRS)', 'description': 'Pain intensity will be evaluated using an 11-point (0-10) Numerical Rating Scale (Pain NRS), which is a simple and easy-to-use measuring scale that consists of a sequence of numbers from zero to 10, in which zero represents "no pain" and 10 represents "the worst pain imaginable". The pain evaluation will be carried out verbally with the patient reporting the pain intensity.', 'timeFrame': '2 weeks after randomization'}

Please estimate the sample size based on the assumption: 
Statistical power of 80%, significance level (alpha) of 5%, and a possible sample loss of up to 15%.
2.22
        Sample size
        The sample size of the study was performed based on the pain intensity outcome (as measured by the pain numerical rating scale) with mean difference of 2.3 points and an estimated standard deviation of 2.76 points.[13] Statistical power of 80% was considered with an alpha of 5% and possible sample loss of up to 15%. Accordingly, a total of 144 patients will be required for the study. The sample calculation was performed using the Minitab software, version 17, (Minitab, Inc., PA).