第1章 概率分布课件.ppt

As a result of this class, you will be able to ... As a result of this class, you will be able to ... 3 65 The sampling distribution is a function of the sample sizes upon which the sample variances are based. Hint: Recall the formula for variance! s2 = S(x -`x)2/(n-1) As a result of this class, you will be able to ... As a result of this class, you will be able to ... As a result of this class, you will be able to ... As a result of this class, you will be able to ... As a result of this class, you will be able to ... :1, 1, 3 3、已知某地COD浓度X ～N(2,32),求COD浓度落的（3，9）的概率。 详见word文档 本章结束，谢谢大家！ As a result of this class, you will be able to ... As a result of this class, you will be able to ... As a result of this class, you will be able to ... As a result of this class, you will be able to ... As a result of this class, you will be able to ... As a result of this class, you will be able to ... As a result of this class, you will be able to ... As a result of this class, you will be able to ... As a result of this class, you will be able to ... As a result of this class, you will be able to ... As a result of this class, you will be able to ... t-分布 (t-distribution) 提出者是William Gosset，也被称为学生分布(student’s t) t 分布是类似正态分布的一种对称分布，通常要比正态分布平坦和分散。一个特定的分布依赖于称之为自由度的参数。随着自由度的增大，分布也逐渐趋于正态分布 x t 分布与标准正态分布的比较 t 分布 标准正态分布 t 不同自由度的t分布 标准正态分布 t (df = 13) t (df = 5) z t-分布(用Excel计算t分布的概率和临界值) ? 用SPSS 计算t分布的临界值 1.3.3 F 分布 为纪念统计学家费希尔(R.A.Fisher) 以其姓氏的第一个字母来命名则 设若U为服从自由度为n1的?2分布，即U~?2(n1)，V为服从自由度为n2的?2分布，即V~?2(n2),且U和V相互独立，则 称F为服从自由度n1和n2的F分布，记为 F-分布(F distribution) 不同自由度的F分布 F (1,10) (5,10) (10,10) F-分布(用SPSS 计算F分布的概率和临街值) 1.4.1 统计量及其分布 1.4.2 样本均值的分布 1.4.3 其他统计量的分布 1.4.4 统计量的标准误差 1.4 样本统计量的概率分布 1.4.1 统计量及其分布 参数和统计量 参数(parameter) 描述总体特征的概括性数字度量，是研究者想要了解的总体的某种特征值； 一个总体的参数：总体均值(?)、标准差(?)、总体比例(?)；两个总体参数：(?1 -?2)、(?1-?2)、(?1/?2)； 总体参数通常用希腊字母表示 ； 统计量(statistic) 用来描述样本特征的概括性数字度量，它是根据样本数据计算出来的一些量，是样本的函数； 一个总体参数推断时的统计量：样本均值(?x)、样本标准差(s)、样本比例(p)等两个总体参数推断