医学统计学英文课件-NonparametricTes.pptVIP

* * * * * * * * * * * * * * * * * Lesson Six Non-parametric test Objectives: 1. To understand the concept and the advantages of Rank Sum Test and master the methods to rank . 2. Factors to determine power. 3. To master the Nonparametric Tests procedures in SPSS. Review The way to draw a conclusion according to t-value in t-test. The way to draw a conclusion according to T-value in Wilcoxon’s signed rank sum test. -3 -2 -1 0 1 2 3 图B 标准正态分布图 P=0.025 P=0.025 x ? -1.96 ? ? +1.96 图A 抽样试验的样本均数分布图 P=0.025 P=0.025 Discussion:1. Which one will you choose to compare two samples, t-test or rank sum test? What’s the reason? 2. If the conditions of t-test are satisfied, compared with t-test for two samples, rank sum test: A More likely to reject H0 B Less likely to reject H0 C The results are the same D The results are different E None of the above 3. When we use rank sum test to compare two samples: A The same sample sizes are required B Rank all the observations one by one orderly and give a mean rank to the same value C Rank all the observations one by one orderly and omit zero D It’s a parametric test if the statistic Z is calculated when the sample sizes are large enough E None of the above 4. What are proper methods to improve power? A Increase sample size. B Increase variation in populations. C Increase the difference between the population means. D Take a lower risk for type I error. E Take a lower risk for type II error. 5. Two medicines were applied to decrease triglyceride in serum. 189 patients with high TG were allocated into groups randomly. The effects were listed as following. One physician processed the data with test. The conclusion was that difference between these two medicines were of statistical significance as α=0.05 . To the same raw data, another physician performed rank sum test. The results were T=9, P0.05.They were not of