求翻译：该研究采用2：1配比的随机双盲试验设计原则，观察3~5月龄、6~23月龄、2~6岁和7~24岁4个年龄组，检测免前、后A、B、C群血清杀菌率抗体水平是什么意思？

The study used a 2:1 ratio of randomized double-blind study design principles, observed 3 to 5 months of age, 6 to 23 months of age, 2 to 6 years old and 7 to 24 years and four age groups, free testing before and after A, B, C group antibody levels in serum bactericidal rate

正在翻译，请等待...

This research uses 2:1 allocated proportion the stochastic double blind experiment principle of design, observes 3~ in May age, 6~23 ages of the moon, 2~6 years old of and 7~24 year old of 4 age groups, the examination exempts before and after A, B, C crowd of blood serum bactericidal coefficient im

The study used the ratio of 2:1 double-blind experimental design principles, looking at six months age and 3-5 months of age, 2~6sui and 7~24sui 4-age group, testing before and after the a, b, c-rates of serum bactericidal antibody level

Using ratio of 2:1 randomized double blind experimental design principles, observe the 3-5 age 6-23 months old, 7~24sui 4 age groups and 2~6sui, detection from front, a, after b, c serum bactericidal antibody level of rates