student’s t test.ppt
《student’s t test.ppt》由会员分享,可在线阅读,更多相关《student’s t test.ppt(26页珍藏版)》请在三一文库上搜索。
1、Students t test,This test was invented by a statistician working for the brewer Guinness. He was called WS Gosset (1867-1937), but preferred to keep anonymous so wrote under the name “Student”.,The t-distribution,William Gosset lived from 1876 to 1937 Gosset invented the t -test to handle small samp
2、les for quality control in brewing. He wrote under the name “Student“.,t-Statistic,When the sampled population is normally distributed, the t statistic is Student t distributed with n-1 degrees of freedom.,T-test,Test for single mean Whether the sample mean is equal to the predefined population mean
3、 ? 2. Test for difference in means Whether the CD4 level of patients taking treatment A is equal to CD4 level of patients taking treatment B ? 3. Test for paired observation Whether the treatment conferred any significant benefit ?,T- test for single mean,The following are the weight (mg) of each of
4、 20 rats drawn at random from a large stock. Is it likely that the mean weight for the whole stock could be 24 mg, a value observed in some previous work?.,9 18 21 26 18 22 27 19 22 29 19 24 30 16 20 24 32,Steps for test for single mean,Questioned to be answered Is the Mean weight of the sample of 2
5、0 rats is 24 mg? N=20, =21.0 mg, sd=5.91 , =24.0 mg 2. Null Hypothesis The mean weight of rats is 24 mg. That is, The sample mean is equal to population mean. 3. Test statistics - t (n-1) df 4. Comparison with theoretical value if tab t (n-1) cal t (n-1) accept Ho, 5. Inference,t test for single mea
6、n,Test statistics n=20, =21.0 mg, sd=5.91 , =24.0 mg t = t .05, 19 = 2.093 Accept H0 if t = 2.093,Inference : There is no evidence that the sample is taken from the population with mean weight of 24 gm,Determining the p-Value,.95,t,0,f(t),-1.96,1.96,.025,.025,red area = rejection region for 2-sided
7、test,Given below are the 24 hrs total energy expenditure (MJ/day) in groups of lean and obese women. Examine whether the obese womens mean energy expenditure is significantly higher ?.,Lean 6.1 7.0 7.5 7.5 5.5 7.6 7.9 8.1 8.1 8.1 8.4 10.2 10.9,T-test for difference in means,Obese 8.8 9.2 9.2 9.7 9.7
- 配套讲稿:
如PPT文件的首页显示word图标,表示该PPT已包含配套word讲稿。双击word图标可打开word文档。
- 特殊限制:
部分文档作品中含有的国旗、国徽等图片,仅作为作品整体效果示例展示,禁止商用。设计者仅对作品中独创性部分享有著作权。
- 关 键 词:
- students test student
链接地址:https://www.31doc.com/p-5177018.html