Here is the design of a clinical trial:

Official Title: Cognitive Behavioral Therapy to Improve Quality of Life After Surgical Treatment of Women With Endometriosis

Included conditions:
- Endometriosis
- Quality of Life
- Pain

Study Armgroups:
- {'label': 'Cognitive behavioral therapy group', 'type': 'EXPERIMENTAL', 'description': 'Patients in this group will undergo a total of 7 sessions of CBT in 5 months in addition to usual care.', 'interventionNames': ['Behavioral: Cognitive behavioral therapy']}
- {'label': 'Usual care', 'type': 'NO_INTERVENTION', 'description': 'Patients in this group will undergo usual care only.'}

Interventions:
- {'type': 'BEHAVIORAL', 'name': 'Cognitive behavioral therapy', 'description': 'Patients in the CBT group will receive usual care. In addition, they will undergo one pre-surgery and six post-surgery face-to-face sessions of CBT. In the pre-surgery session, management of expectations towards surgery will be addressed. In the six post-surgery sessions, attention will be paid to psycho-education concerning the biological link between endometriosis-related pain and stress, relaxation training, cognitive stress management, and management of anxiety, catastrophizing and hypervigilance. The CBT sessions will be coordinated by a registered psychotherapist who is experienced in CBT and has knowledge about endometriosis. All CBT will be individual sessions.', 'armGroupLabels': ['Cognitive behavioral therapy group']}

Primary Outcomes:
- {'measure': 'Change in Health Related Quality of Life assessed by the Endometriosis Health Profile 30', 'description': 'The Endometriosis Health Profile 30 (EHP-30) is a disease-specific QoL questionnaire which is validated for use in endometriosis patients and measures the impact of the disease on physical, mental and social aspects of life.\n\nThe EHP-30 is not a numerical scale.', 'timeFrame': '7,5 months'}
- {'measure': 'Change in general Quality of Life assessed by the Short Form 36', 'description': 'The Short Form 36 (SF-36) is a multipurpose, general health survey which is applied to measure QoL on nine different domains: physical functioning, social functioning, role limitations due to physical health, role limitations due to emotional problems, emotional well-being, vitality, pain, general health, and health change.\n\nThe SF-36 is not a numerical scale.', 'timeFrame': '7,5 months'}

Please estimate the sample size based on the assumption: 
Significance level (α) = 0.05, power (1-β) = 0.85, and a dropout rate of 19%.
Sample size calculation
          The calculation for the required sample size was performed for the primary endpoint QoL. There was no study available describing the effect size of CBT on QoL after endometriosis surgery which could be used in the sample size calculation. Therefore, we used a study in which the authors examine a cognitive behavioural intervention to improve QoL in patients undergoing surgery due to chronic back pain.13 Based on this article we expect to find medium to large effect sizes (Cohenâs d) of 0.75 and 1.35 (measured with the physical and mental component scales of the 12-Item Short-Form Health Survey) of postoperative CBT compared with usual care-only on QoL regarding physical and mental health, respectively. Based on literature we expect the dropout rate to be 15%â16%.14 15 However, due to the intensity of the intended intervention combined with surgery we anticipating patient dropout to be higher: 19%. Therefore, a total of 100 patients should be included to detect significant effects (Î±=0.05, power (1-Î²)=0.85).