Variance -方差
方差就是一组数据中平均值与任意点之间的距离。
The Variance is the distance between the mean of a set of data to any point in the data. Lets say you have a process whose output are bags whose lengths are
10, 10.5 , 10.23 , 10.21 , 11.23, 11, 10.11
The average is - 10.46 & Variance is 0.222 - Which means that any data point in the above mentioned data set is away from the mean by 0.222 units .
Variation -差异
正常预期结果与观测结果之间的差额总量即为差异
The amount of difference between a normal expected output to the observed output is variation.
Example -
You expect to produce a product (Like the above example) whose length is 10 Units (This is the expected standard you are trying to acheive) but you might end up producing bags that are slightly bigger or smaller. this is the variation,This could be due to a variety of reasons ex - the skill and exp of the workman,faulty machines etc..The ways to measure this variation could be variance ,Standard Deviation and Range
Standard Deviation -标准偏差
This is relatively simple.this would be the square root of variance and denoted by the symbol Sigma and this forms the basis of Six Sigma which aims to reduce the variation in the process.
Let me know if this makes sense.
Regards,
Khader
[此贴子已经被作者于2008-10-29 15:10:20编辑过]
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