第三章样本均数的抽样误差与置信区间.doc

第三章样本均数的抽样误差与置信区间
★联系：
数据/变量在离散点或区间上分布分布特征数应用样本数据x频数分布表频数分布图描述指标()参考值范围
随机变量X
,误差概率分布表概率分布图总体参数()
()置信区间

3.1样本均数的分布

·从同一总体中独立抽取多份样本,他们的均数常大小不一,这说明样本均数存在变异。通过电脑实验来认识样本均数的变异规律
一、正态总体样本均数的分布
实验3.1从正态分布总体抽样的实验假定正常男子的红血球计数服从正态分布N(4.6602,0.57462)，随机抽取1000份样本,每份含n＝5个个体。样本均数依然是一个随机变量,且
(1)各样本均数未必等于总体均数(，误差？)；
(2)样本均数之间存在差异(，变异)；
(3)样本均数的分布很有规律,围绕着总体均数,中间多、两边少,左右基本对称(对称、正态？)；
(4)样本均数的变异范围较原变量变异范围大大缩小()；
(5)随着样本量的增大,样本均数变异范围逐渐缩小()。
图3.1从正态分布总体抽样的实验结果
原正态总体N(4.6602,0.57462)；直方图是样本均数的分布
（Luo:这里横坐标为，若改为便是误差分布—图的形状不变）
3.7
4.1
4.5
4.9
5.3
5.7
3.7
4.1
4.5
4.9
5.3
5.7
3.7
4.1
4.5
4.9
5.3
5.7
n=5n=10n=30
(a)(b)(c)
HYPERLINK\l"表3_2"表3_2

HYPERLINK\l"实3_1a"实3_1a表3.1从N(4.6602,0.57462)中随机抽样,样本量为5,100份独立
样本的均数、标准差和总体均数的95%置信区间(单位：1012/L)
样本
号均数标准差95%置信区间样本
号均数标准差95%置信区间15.00.56884.2939,5.7062514.48.40063.9827,4.977324.72.34704.2891,5.1509524.32.54873.6388,5.001234.24.57633.5246,4.9554534.88.37324.4167,5.343444.64.59493.9014,5.3786544.68.35244.2425,5.117554.60.40054.1028,5.0972554.80.58664.0717,5.528364.80.81863.7837,5.8163564.52.35044.0850,4.955074.68.45024.1211,5.2389574.88.68694.0272,5.732884.32.82253.2989,5.3411584.80.52324.1505,5.449594.72.59643.9796,5.4604594.80.27944.4531,5.1469104.40.44963.8418,4.9582604.76.58234.0371,5.4830114.60.56833.8944,5.3056614.76.70833.8807,5.6394124.60.34014.1778,5.0222624.12.57933.4008,4.8392134.60.66483.7746,5.4254634.72.44194.1714,5.2686144.76.62743.9811,5.5389644.44.28184.0902,4.7898154.20.68863.3451,5.0549654.921.02673.6454,6.1947164.64.30914.2562,5.0238664.80.71913.9073,5.6927174.96.42234.4357,5.4843674.72.43614.1786,5.2614184.96.40834.4532,5.4669684.84.58734.1109,5.5691194.68.58753.9506,5.4094694.36.48923.7527,4.9673204.84.53404.1771,5.5030704.76.33534.3437,5.1763214.92.28524.5659,5.2741714.40.43093.8650,4.9350224.60.45174.0392,5.1608724.68.68803.8259,5.5341234.44.43333.9021,4.9779734.60.43014.0661,5.1339244.96.37114.4993,5.4207744.48.64113.6841,5.2759254.64.47424.0513,5.228775*4.16.39273.6724,4.6476264.96.53494.2959,5.6241764.