Here is the design of a clinical trial:

Official Title: Timing of Transcranial Direct Current Stimulation (tDCS) Combined With Speech and Language Therapy (SLT): An Intervention Development Study for Aphasia

Included conditions:
- Aphasia

Study Armgroups:
- {'label': 'Offline tDCS-before therapy', 'type': 'ACTIVE_COMPARATOR', 'description': 'Participants will receive 20 minutes of tDCS prior to the 40 minute speech-language therapy session.', 'interventionNames': ['Device: Offline tDCS-before therapy']}
- {'label': 'Offline tDCS-after therapy', 'type': 'ACTIVE_COMPARATOR', 'description': 'Participants will receive 20 minutes of tDCS after the 40 minute speech-language therapy session.', 'interventionNames': ['Device: Offline tDCS-after therapy']}
- {'label': 'Online tDCS', 'type': 'ACTIVE_COMPARATOR', 'description': 'tDCS will be applied at the beginning of the 40 minute speech-language therapy session and will last for 20 minutes.', 'interventionNames': ['Device: Online tDCS']}
- {'label': 'Sham tDCS', 'type': 'SHAM_COMPARATOR', 'description': 'Sham tDCS will be applied at the beginning of the 40 minute speech-language therapy session.', 'interventionNames': ['Device: Sham tDCS']}

Interventions:
- {'type': 'DEVICE', 'name': 'Offline tDCS-before therapy', 'description': 'Direct current stimulation will be delivered using a battery-driven constant current stimulator. 2mA of direct current will be applied for 20 minutes to the angular gyrus region of the brain. We will use a standard-of-care treatment - script training - to provide speech-language therapy to our subjects. The scripting treatment will be delivered by a computer program that provides script training in an interactive conversational context.', 'armGroupLabels': ['Offline tDCS-before therapy']}
- {'type': 'DEVICE', 'name': 'Sham tDCS', 'description': 'Stimulation will be given for a total 30 seconds (including ramp-up and ramp-down of current) and then the tDCS device will be turned off. The brief stimulation will produce tDCS-induced sensation so that participants will not be aware when the tDCS was turned off .We will use standard-of-care treatment - script training - to provide speech-language therapy to our subjects. The scripting treatment will be delivered by a computer program that provides script training in an interactive conversational context.', 'armGroupLabels': ['Sham tDCS']}
- {'type': 'DEVICE', 'name': 'Offline tDCS-after therapy', 'description': 'Direct current stimulation will be delivered using a battery-driven constant current stimulator. 2mA of direct current will be applied for 20 minutes to the angular gyrus region of the brain. We will use a standard-of-care treatment - script training - to provide speech-language therapy to our subjects. The scripting treatment will be delivered by a computer program that provides script training in an interactive conversational context.', 'armGroupLabels': ['Offline tDCS-after therapy']}
- {'type': 'DEVICE', 'name': 'Online tDCS', 'description': 'Direct current stimulation will be delivered using a battery-driven constant current stimulator. 2mA of direct current will be applied for 20 minutes to the angular gyrus region of the brain. We will use a standard-of-care treatment - script training - to provide speech-language therapy to our subjects. The scripting treatment will be delivered by a computer program that provides script training in an interactive conversational context.', 'armGroupLabels': ['Online tDCS']}

Primary Outcomes:
- {'measure': 'Change in trained conversational script.', 'description': 'Changes in accuracy and rate of production on a trained conversational script from pre to post-treatment.', 'timeFrame': '3 weeks.'}

Please estimate the sample size based on the assumption: 
Two-tailed analyses with a significance level (Î±) of 0.05, 80% power, and a two-sample t-test. The precision of the estimate is a half-width of a 95% confidence interval of ±5.2%.
Sample size and power
        The study will enroll a total of 48 subjects (12 in each group). Power calculations were based on our previous work with similar participants, and planned two-tailed analyses (Î± = .05) for the primary outcome measure, the simulated conversation on the trained script.
        In preliminary work without tDCS, we observed improvement in trained script accuracy at the end of language treatment relative to baseline was 10.4% (SD = 8.2%). Assuming similar variability in the proposed study, n = 12 subjects per group will allow us to estimate changes in accuracy with precision (half-width of a 95% confidence interval) of Â±5.2% in each group. In addition, a sample size of n = 12 subjects per group will provide 80% power with two-sided Î±â=â0.5 for a two-sample t-test to detect a 9.9% difference in accuracy improvement between treatment arms and the sham treatment (e.g., improvement in accuracy of 10.4% and 20.3% in the two arms, respectively).