Here is the design of a clinical trial:

Official Title: Cost-effectiveness and Cost-Utility Evaluation of the Individual vs. Group Transdiagnostic Psychological Treatment for Emotional Disorders in Primary Care (PsicAP-Costs)

Included conditions:
- Emotional Disorder
- Depression
- Somatoform Disorders
- Anxiety Disorders

Study Armgroups:
- {'label': 'Group 1', 'type': 'EXPERIMENTAL', 'interventionNames': ['Other: Group brief transdiagnostic cognitive-behavioral therapy']}
- {'label': 'Group 2', 'type': 'EXPERIMENTAL', 'interventionNames': ['Other: Individual brief transdiagnostic cognitive-behavioral therapy']}
- {'label': 'Group 3', 'type': 'ACTIVE_COMPARATOR', 'interventionNames': ['Other: Treatment as usual']}

Interventions:
- {'type': 'OTHER', 'name': 'Group brief transdiagnostic cognitive-behavioral therapy', 'description': 'An adaptation of the Unified Protocol for the Transdiagnostic Treatment of Emotional Disorders (UP) (Barlow et al., 2015) and the IAPT programme (Clark, 2018). It has been developed by Cano-Vindel (González-Blanch et al., 2018) and consists in seven 90-minute sessions, provided by a non-assessor clinical psychologist in 12-16 weeks, with 8-10 participants per group. Sessions are weekly or biweekly, reducing their frequency as the intervention advances. The activities and homework proposed are supported with materials such as theory documents, a CD for progressive muscle relaxation, self-recording sheets, and a therapy web (www.desordenesemocionales.es).', 'armGroupLabels': ['Group 1'], 'otherNames': ['Group tCBT']}
- {'type': 'OTHER', 'name': 'Individual brief transdiagnostic cognitive-behavioral therapy', 'description': 'An adaption of the group therapy, with the same phases. However, since it is an individual intervention, it is more flexible than group one and its contents and duration can be personalized. This intervention consists of a minimum of 6 and a maximum of 8 sessions of 30-60 minutes, provided by a clinical psychologist not involved in the assessments.', 'armGroupLabels': ['Group 2'], 'otherNames': ['Individual tCBT']}
- {'type': 'OTHER', 'name': 'Treatment as usual', 'description': 'Participants in this group will be provided the common primary care treatment by the GP, in a face-to-face consultation that seldom exceeds 10 minutes. TAU usually consists in pharmacological treatment prescribed by the GP, however, it might also consist in practical advice or even non-treatment (Watts et al., 2015). The first consultation will count as part of the recruitment process and, if the patient accepts to participate in the trial, no therapeutic help will be provided to them until they are allocated. Once in the TAU intervention, if the practitioner recommended any psychological treatment as part of it (e.g., referral to specialized care), the participant would be excluded to avoid contamination between clusters. TAU has not a specific amount of sessions; it will finish when the GP considers the patient is recovered.', 'armGroupLabels': ['Group 3'], 'otherNames': ['TAU']}

Primary Outcomes:
- {'measure': 'Change in depression symptoms: 9-item Patient Health Questionnaire (PHQ-9)', 'description': 'The PHQ-9 (Kroenke et al., 2001) is the depression module of the PHQ (Díez-Quevedo et al., 2001; Spitzer et al., 1999), that scores the 9 DSM-IV depression criteria present in the last two weeks from 0 ("not at all") to 3 ("nearly every day"). A score of 10 is usually set as the cut-off point for major depression disorder (MDD): a score of 10-14 indicates minor depression, moderate MDD, or dysthymia; 15-19, moderately severe MDD; and 20-27, severe MDD. This tool has been tested in Spanish primary care centres (McDonald\'s ω = .89) (Muñoz-Navarro, Cano-Vindel, Medrano et al., 2017), finding 12 as the best cut point for MDD diagnosis (sensitivity of 84% and specificity of 78%) compared with 10 (sensitivity of 95% and specificity of 67%).', 'timeFrame': 'Baseline, immediately after the intervention, and follow-ups (6 and 12 months)'}
- {'measure': 'Change in anxiety symptoms: 7-item General Anxiety Disorder scale (GAD-7)', 'description': 'The GAD-7 (Spitzer et al., 2006) assesses common anxiety symptoms in the last two weeks, scoring from 0 ("not at all") to 3 ("nearly every day"). Cut points of 5, 10, and 15 represent mild, moderate, and severe anxiety, respectively. The algorithm sets 8 as the cut point for GAD, however it has been found that a score of 10 is more optimal (Spitzer et al., 2006). We will use the version validated by García-Campayo et al. (2010), that was recently tested in primary care centres (Cronbach\'s α = .83) (Muñoz-Navarro, Cano-Vindel, Moriana et al., 2017), confirming the score of 10 as the best diagnostic criterion (sensitivity of 87% and specificity of 78%).', 'timeFrame': 'Baseline, immediately after the intervention, and follow-ups (6 and 12 months)'}
- {'measure': 'Change in panic symptoms: Patient Health Questionnaire-Panic Disorder (PHQ-PD)', 'description': 'The PHQ-PD is the specific panic disorder module of the PHQ and scores each DSM-IV criterion as "yes" or "no" (Wittkampf et al., 2011). Muñoz-Navarro et al. (2016) tested it in Spanish primary care settings and modified the original algorithm to increase the sensitivity for PD diagnosis: the most optimal cut-off point for screening purposes was 5 (the first item \\[for panic screening\\] and one of the following three, plus four somatic symptoms) (sensitivity of 77% and specificity of 72%).', 'timeFrame': 'Baseline, immediately after the intervention, and follow-ups (6 and 12 months)'}
- {'measure': 'Change in somatoform symptoms: 15-item Patient Health Questionnaire (PHQ-15)', 'description': 'The PHQ-15 (Kroenke et al., 2002) is the somatization module of the PHQ. It includes 13 somatic symptoms plus 2 from the PHQ-9 (sleeping problems and fatigue). Scores of 5, 10, and 15 represent low, medium, and high somatic symptom severity, respectively. To screen a somatization disorder, whereas the original algorithm needs of at least a score of 2 in three or more somatic symptoms (sensitivity of 78% and specificity of 71%) (van Ravesteijn et al., 2009), the cut point usually used is 10; nevertheless, since this can be obtained with ten symptoms of mild severity, we decided to join both criteria to screen the disorder. Furthermore, an absence of biological cause is also often required (since PHQ-15 does not distinguish between medically explained and unexplained symptoms) (Kroenke et al., 2002), but the self-administered nature of the PHQ-15 makes difficult to determine this. The PHQ-15 has been validated with Spanish psychiatric outpatients (α = .78) (Ros et al., 2010).', 'timeFrame': 'Baseline, immediately after the intervention, and follow-ups (6 and 12 months)'}

Please estimate the sample size based on the assumption: 
An effect size of .3 (f value), a statistical power of .8, a significance level of .05, and a dropout rate of 15% were assumed.
Sample size
        We used effect sizes from the previous literature to determine the sample size. Corpas et al.âs primary care RCT [41] compared both group and individual brief tCBT with TAU for emotional disorders and found low to medium effect sizes for all outcomes. Individual effects were larger (Cohenâs d ranged from .54 to .74) than group effects (.4 to .63) when compared with TAU; however, there was no significant difference between both transdiagnostic formats, with (very) low effect sizes (.06 to .27). Another primary RCT by Corpas et al. [36] compared tCBT with TAU and found medium to large effect sizes (from .39 for depression to .81 for panic symptoms). Finally, the PsicAP study compared the group tCBT used herein to TAU in primary care. Intention-to-treat analyses showed low to medium effect sizes over time for depression (Morrisâ d ranged from .36 to .58), anxiety (.38 to .65), and somatizations (.31 to .4). Subsequently, we decided to assume a medium effect size of .6 (Cohenâs d).
        Since software to determine sample sizes for linear mixed model analyses was not available, we used the f index of G*Power [52]. We assumed an effect size of .3 (the equivalent f value); a statistical power (1 - Î²) of .8; and a significance level (Î±) of .05, obtaining a required sample size of 111. However, to control withdrawals and take into account the abandonment rates in other similar trials [36, 41], we assumed a dropout rate of 15%, which brought the required sample size to 128.