56只新西兰大白兔随机分为3组用于胸部损伤特点及心肺功能研究：假致伤组12只；实验一组22只；实验二组22只。伤前及伤后3h、6h、12h抽取动脉血行心肌标记物及血气分析（CK-MB，cTnI；PO2，PCO2，乳酸）。
审稿人问题：Theauthors state that they performed a repeated measures ANOVA, but given that they have both within and between subject measures, what they needed to performwas a mixed repeated measures ANOVA. Reviewer has some concerns with the statistical analyses such as the treatment of the sham group, the handling of uneven between groups sizes. 审稿人让我使用混合模型并问我假致伤组只有12只动物，采用什么统计方法处理组间的不均衡性？