在"英语"词典里mean}的意思

在数学中，根据上下文，意思有几个不同的定义。 在概率和统计学中，平均值和期望值被同义地用于指概率分布或以该分布为特征的随机变量的中心趋势的一个度量。 在随机变量X的离散概率分布的情况下，平均值等于由该值的概率加权的每个可能值的和; 也就是说，通过将X的每个可能值x及其概率P的乘积进行计算，然后将所有这些乘积相加在一起。 类似的公式适用于连续概率分布的情况。 不是每个概率分布都有一个定义的平均值 以柯西分布为例。 此外，对于某些分布，平均值是无穷大的：例如，当值的概率为n = 1,2,3，...时， In mathematics, mean has several different definitions depending on the context. In probability and statistics, mean and expected value are used synonymously to refer to one measure of the central tendency either of a probability distribution or of the random variable characterized by that distribution. In the case of a discrete probability distribution of a random variable X, the mean is equal to the sum over every possible value weighted by the probability of that value; that is, it is computed by taking the product of each possible value x of X and its probability P, and then adding all these products together, giving. An analogous formula applies to the case of a continuous probability distribution. Not every probability distribution has a defined mean; see the Cauchy distribution for an example. Moreover, for some distributions the mean is infinite: for example, when the probability of the value is for n = 1, 2, 3,....