推荐回答(5个)
不对,表示数据离散程度的是方差。方差是在概率论和统计方差衡量随机变量或一组数据时离散程度的度量。
在统计描述中,方差用来计算每一个变量(观察值)与总体均数之间的差异。为避免出现离均差总和为零,离均差平方和受样本含量的影响,统计学采用平均离均差平方和来描述变量的变异程度。总体方差计算公式:
![](/picurl?url=https%3A%2F%2Fiknow-pic.cdn.bcebos.com%2Fa8ec8a13632762d0d3d568c9afec08fa503dc6d9%3Fx-bce-process%3Dimage%252Fresize%252Cm_lfit%252Cw_600%252Ch_800%252Climit_1%252Fquality%252Cq_85%252Fformat%252Cf_auto)
σ^2为总体方差,X为变量,μ为总体均值,N为总体例数。
扩展资料:
方差的性质
1、设C是常数,则D(C)=0
2、设X是随机变量,C是常数,则有
![](/picurl?url=https%3A%2F%2Fiknow-pic.cdn.bcebos.com%2Fd0c8a786c9177f3ed465337b7fcf3bc79f3d5677%3Fx-bce-process%3Dimage%252Fresize%252Cm_lfit%252Cw_600%252Ch_800%252Climit_1%252Fquality%252Cq_85%252Fformat%252Cf_auto)
3、设 X 与 Y 是两个随机变量,则
![](/picurl?url=https%3A%2F%2Fiknow-pic.cdn.bcebos.com%2Fae51f3deb48f8c541eb80a5935292df5e0fe7f59%3Fx-bce-process%3Dimage%252Fresize%252Cm_lfit%252Cw_600%252Ch_800%252Climit_1%252Fquality%252Cq_85%252Fformat%252Cf_auto)
其中协方差
![](/picurl?url=https%3A%2F%2Fiknow-pic.cdn.bcebos.com%2Fd4628535e5dde71110fd8c80a8efce1b9d16619d%3Fx-bce-process%3Dimage%252Fresize%252Cm_lfit%252Cw_600%252Ch_800%252Climit_1%252Fquality%252Cq_85%252Fformat%252Cf_auto)
特别的,当X,Y是两个不相关的随机变量则
![](/picurl?url=https%3A%2F%2Fiknow-pic.cdn.bcebos.com%2Fb8014a90f603738d54e5c354bc1bb051f819ec1e%3Fx-bce-process%3Dimage%252Fresize%252Cm_lfit%252Cw_600%252Ch_800%252Climit_1%252Fquality%252Cq_85%252Fformat%252Cf_auto)
此性质可以推广到有限多个两两不相关的随机变量之和的情况。
4、D(X)=0的充分必要条件是X以概率1取常数E(X),即
![](/picurl?url=https%3A%2F%2Fiknow-pic.cdn.bcebos.com%2F7e3e6709c93d70cf8dab657bf7dcd100baa12b77%3Fx-bce-process%3Dimage%252Fresize%252Cm_lfit%252Cw_600%252Ch_800%252Climit_1%252Fquality%252Cq_85%252Fformat%252Cf_auto)
(当且仅当X取常数值E(X)时的概率为1时,D(X)=0。)
注:不能得出X恒等于常数,当x是连续的时候X可以在任意有限个点取不等于常数c的值。
5、D(aX+bY)=a2DX+b2DY+2abCov(X,Y)。
平均数越大说明数据的离散程度越大是错误的。
平均数,统计学术语,是表示一组数据集中趋势的量数,是指在一组数据中所有数据之和再除以这组数据的个数。它是反映数据集中趋势的一项指标。解答平均数应用题的关键在于确定“总数量”以及和总数量对应的总份数。
平均数是统计学中最常用的统计量,用来表明资料中各观测值相对集中较多的中心位置。在统计工作中,平均数(均值)和标准差是描述数据资料集中趋势和离散程度的两个最重要的测度值。
方差越大说明数据的离散程度越大,即:
当数据分布比较分散(即数据在平均数附近波动较大)时,各个数据与平均数的差的平方和较大,方差就较大;当数据分布比较集中时,各个数据与平均数的差的平方和较小。因此方差越大,数据的波动越大;方差越小,数据的波动就越小。
![](/picurl?url=https%3A%2F%2Fiknow-pic.cdn.bcebos.com%2F6159252dd42a2834b7e6c27d54b5c9ea15cebf00%3Fx-bce-process%3Dimage%252Fresize%252Cm_lfit%252Cw_600%252Ch_800%252Climit_1%252Fquality%252Cq_85%252Fformat%252Cf_auto)
扩展资料
平均数的几种类型
1、算术平均数
算术平均数是指在一组数据中所有数据之和再除以数据的个数。它是反映数据集中趋势的一项指标。把n个数的总和除以n,所得的商叫做这n个数的算术平均数。
2、几何平均数
n个观察值连乘积的n次方根就是几何平均数。根据资料的条件不同,几何平均数分为加权和不加权之分。
3、调和平均数
调和平均数是平均数的一种。但统计调和平均数,与数学调和平均数不同。在数学中调和平均数与算术平均数都是独立的自成体系的。计算结果两者不相同且前者恒小于后者。
4、指数平均数
指数平均数[EXPMA],其构造原理是对股票收盘价进行算术平均,并根据计算结果来进行分析,用于判断价格未来走势得变动趋势。
参考资料:百度百科-方差
百度百科-平均数
兄弟应该是搞错了,变异系数越小,变异程度越小(波动越小)。
1.简而言之,CV值就是去除量纲后的标准差,标准差除以均值得到的,没有单位,可以直观地对数据进行简易分析;
2.用CV值对数组平行试验结果进行测算,进而推断总体即试验数据离散程度,属于描述性统计。
3.一般而言,根据不同的总体,计算CV值不能少于3个数据,最好能在10个以上,样本量过大时用CV进行推断的准确度就不够了。
4.对于工艺路线已运行一段时间,不是处于摸索阶段,CV值可参考以下内容进行推断:当CV值小于1%时,表示数据离散程度较小;在1%-2%之间,表示数据离散度正常;在2%-3%,表示数据离散度尚可接受;当大于4%时,表示数据离散度较大;数据越大表明工艺路线越不稳定。
5.对于处于摸索阶段的工艺路线,一般认为若用CV值推断总体,低于10%其推断离散程度是可以接受的。
但需说明的是,由于CV值仅仅是描述性统计,要想得到更准确的数据波动性、过程能力或显著性差异推断,建议采用SPC、CPK、假设检验、方差分析、趋势分析等工具。
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