Here is the design of a clinical trial:

Official Title: A Randomized Trial Comparing the Effect of Immediate Versus Delayed Frozen-thawed Embryo Transfer Following a Stimulated IVF Cycle

Included conditions:
- Fertilization in Vitro
- Embryo Transfer

Study Armgroups:
- {'label': 'immediate group', 'type': 'OTHER', 'description': 'the intervention: immediate frozen-thawed embryo transfer (FET) which means FET will be performed in the first cycle following the stimulated IVF cycle', 'interventionNames': ['Other: immediate frozen-thawed embryo transfer']}
- {'label': 'delayed group', 'type': 'OTHER', 'description': 'the intervention: delayed frozen-thawed embryo transfer (FET) which means FET will be performed at least in the second cycle following the stimulated IVF cycle', 'interventionNames': ['Other: delayed frozen-thawed embryo transfer']}

Interventions:
- {'type': 'OTHER', 'name': 'immediate frozen-thawed embryo transfer', 'description': 'Frozen-thawed embryo transfer will be performed in the first cycle following the stimulated IVF cycle', 'armGroupLabels': ['immediate group']}
- {'type': 'OTHER', 'name': 'delayed frozen-thawed embryo transfer', 'description': 'Frozen-thawed embryo transfer will be performed at least in the second cycle following the stimulated IVF cycle', 'armGroupLabels': ['delayed group']}

Primary Outcomes:
- {'measure': 'ongoing pregnancy', 'description': 'viable pregnancy beyond gestation 12 weeks', 'timeFrame': 'viable pregnancy beyond gestation 12 weeks'}

Please estimate the sample size based on the assumption: 
Power of 0.8, type I error of 0.05, and a 10% drop-out rate.
Sample size calculations and statistical analysis
        
          Sample size estimation
          According to our data of the centre, the ongoing pregnancy rate per FET was about 30%. We hypothesise that a difference in the ongoing pregnancy rate of 10% between the immediate versus delayed groups as equivalence, the sample size required for a test of equivalence would be 329 in each arm to give a power of 0.8 and type I error of 0.05. Allowing 10% drop-out, 724 subjects or 362 in each arm will be needed.
        
        
          Data analysis
          Data will be analysed with an intention to treat and per protocol. Demographic features of the two groups will be compared. Comparison of quantitative variables will be performed using Studentâs t-test, while categorical variables will be compared using a Ï2 analysis. If randomisation fails to achieve two balanced groups, we will use the multivariable logistic regression to adjust for potentially confounding factors and results, namely female age (as a continuous variable), failed fresh ET or freeze-all, retrieved oocytes, COH protocol, ovulation trigger, number of good-quality embryos produced (as a continuous variable) and number of embryos transferred (one vs two), developmental stage (cleavage vs blastocyst stage) and quality of the embryos transferred (quality of the embryo transferred). If the primary unadjusted analysis and secondary adjusted analysis are discordant, we will give greater weighting to the primary analysis in the interpretation of trial findings.
          All statistical analyses of the data will be performed using the SPSS program V.21.0 (SPSS), and a p value <0.05âwill be considered statistically significant.