热度 2|
Kruskal-Wallis Test
Kruskal-Wallis Test在临床试验中常用来比较三个Wilcoxon Rank-Sum Test或三个以上剂量组或治疗组非正态分布变量的比较。
Cohen Reis E, Holubkov R. Vapocoolant spray is equally effective as EMLA cream in reducing immunization pain in school-aged children. Pediatrics. 1997 Dec;100(6):E5.
“Histograms were prepared for the main outcome variables, the subject pain measures. As these histograms revealed that the data were not distributed along a normal curve, nonparametric tests were used to assess differences between treatment groups. Specifically, for continuous and ordinal level data, the Kruskal-Wallis test was used to test for differences between all three groups”
同样地,Kruskal-Wallis Test也是非参数检验方法,是基于观察值的秩,而不是实际观察值。其基本思路与Wilcoxon Rank-Sum Test类似,把所有治疗组的观察值混合在一起,对每个观察值进行排序编秩,于是可计算得出每个治疗组的平均秩,若治疗组间没有差异,那么不同治疗组的平均秩应该近似,否则如果平局秩相差较大,则说明至少有两组有差异。具体检验方法,可参见相关书籍,小胖在此不做赘述。下边是Kruskal-Wallis Test的SAS程序:
PROC NPAR1WAY WILCOXON;
CLASS TREAT;
VAR SCORE;
RUN;
我们可以看出Kruskal-Wallis Test的SAS程序与Wilcoxon Rank-Sum Test一样,不同的是在看结果时,Kruskal-Wallis Test要看SAS ouput中Kruskal-Wallis Test部分的结果。
当Kruskal-Wallis Test显示有统计学意义时,可以进而采用Wilcoxon Rank-Sum Test来进行组间的两两比较,但这时必须考虑到I类错误的增加,要对p值进行调整。
手机版|会员|至尊|接种|公卫人 ( 沪ICP备06060850号-3 )
GMT+8, 2024-5-16 03:58 , Processed in 0.029224 second(s), 6 queries , Gzip On, MemCached On.
Powered by Discuz! X3.4
© 2001-2023 Discuz! Team.