Sample size calculation
Anderson & Lambert
RECRUITMENT
The power analysis was conducted by ‘G*Power’. A previous meta-analysis demonstrated that the effect sizes of short-term dynamic therapy were 0.71 and 0.34 (Anderson & Lambert, We planned to complete recruitment by April 2021. However, recruitment was negatively affected by the COVID-19 pandemic and the recruitment period was extended to December 2021. To avoid the discontinuity caused by excessive extension, which may affect the overall research progress, our final recruitment number in each group was close to but not over 80. No interim data analysis was performed that informed our decision to stop recruitment.