Here is the design of a clinical trial:

Official Title: Neuromodulation Through Brain Stimulation-assisted Cognitive Training in Patients With Post-COVID-19 Cognitive Impairment

Included conditions:
- COVID-19
- Post-COVID-19

Study Armgroups:
- {'label': 'Anodal tDCS + cognitive training', 'type': 'EXPERIMENTAL', 'description': 'device: anodal transcranial direct current stimulation (tDCS), 9 sessions with 20 minutes stimulation each (2 mA) over left dorsolateral prefrontal cortex\n\nbehavioral: intensive cognitive training intensive cognitive training of letter memory updating task (20 minutes), 9 sessions', 'interventionNames': ['Device: Anodal tDCS', 'Behavioral: Intensive cognitive training']}
- {'label': 'Sham tDCS + cognitive training', 'type': 'PLACEBO_COMPARATOR', 'description': 'device: sham transcranial direct current stimulation (tDCS), 9 sessions with 30 seconds stimulation each (2 mA) over left dorsolateral prefrontal cortex\n\nbehavioral: intensive cognitive training intensive cognitive training of letter memory updating task (20 minutes), 9 sessions', 'interventionNames': ['Device: Sham tDCS', 'Behavioral: Intensive cognitive training']}
- {'label': 'Sham tDCS + Progressive Muscle Relaxation training', 'type': 'ACTIVE_COMPARATOR', 'description': 'device: sham transcranial direct current stimulation (tDCS), 9 sessions with 30 seconds stimulation each (2 mA) over left dorsolateral prefrontal cortex\n\nbehavioral: progressive muscle relaxation (PMR) standardized instructed PMR (20 minutes), 9 sessions', 'interventionNames': ['Device: Sham tDCS', 'Behavioral: Progressive muscle relaxation (PMR)']}

Interventions:
- {'type': 'DEVICE', 'name': 'Anodal tDCS', 'description': 'Anodal transcranial direct current stimulation (tDCS), 9 sessions with 20 minutes stimulation each (2 mA)', 'armGroupLabels': ['Anodal tDCS + cognitive training']}
- {'type': 'DEVICE', 'name': 'Sham tDCS', 'description': 'Sham transcranial direct current stimulation (tDCS), 9 sessions with 30 sec stimulation each (2 mA) to ensure blinding of participants', 'armGroupLabels': ['Sham tDCS + Progressive Muscle Relaxation training', 'Sham tDCS + cognitive training']}
- {'type': 'BEHAVIORAL', 'name': 'Intensive cognitive training', 'description': 'Intensive cognitive training of a letter memory updating task, 9 sessions', 'armGroupLabels': ['Anodal tDCS + cognitive training', 'Sham tDCS + cognitive training']}
- {'type': 'BEHAVIORAL', 'name': 'Progressive muscle relaxation (PMR)', 'description': 'Standardized instructed PMR training, 9 sessions', 'armGroupLabels': ['Sham tDCS + Progressive Muscle Relaxation training']}

Primary Outcomes:
- {'measure': 'Working memory performance at post-assessment', 'description': 'Percent change of correct responses in the n-back task compared to the pre-training assessment.', 'timeFrame': '3 weeks'}

Please estimate the sample size based on the assumption: 
A two-sided significance level of α=0.05 and a power of at least 80%.
Sample size
          Power calculation is based on recent studies using multisession application of cognitive training compared with a control training on immediate performance in the trained task (primary outcome).49â51 Based on these data, we estimated an effect size of 0.8 (Cohenâs d). To demonstrate an effect in the primary outcome between cognitive training groups and control (% correct in the n-back task for training groups vs PMR group) with an independent t-test using a two-sided significance level of Î±=0.05âand a power of at least 80%, 60 participants (40 for cognitive training groups (for secondary comparison of training plus anodal vs sham tDCS groups), 20 for PMR group) need to be included. This conservative approach using a t-test was chosen, even though we intend to analyse the primary outcome conducting analysis of covariance models.52 This monocentric clinical trial will serve to calculate the sample size for a subsequent multicentre clinical trial. Sample size estimation was conducted using R software (http://www.R-project.org) and the pwr package (https://cran.r-project.org/package=pwr).