secondmoment是什么意思,查了下说是二阶矩,还是不懂

Question

second moment是什么意思,查了下说是二阶矩,还是不懂

Answer 1

数学中矩的概念来自于物理学.在物理学中,矩是用来表示物体形状的物理量.矩是用于物体形状识别的重要参数指标.
In mathematics,the second moment method is a technique used in probability theory and analysis to show that a random variable has positive probability of being positive.More generally,the "moment method" consists of bounding the probability that a random variable fluctuates far from its mean,by using its moments.[1]
The method is often quantitative,in that one can often deduce a lower bound on the probability that the random variable is larger than some constant times its expectation.The method involves comparing the second moment of random variables to the square of the first momen