求翻译：样本时间序列展现了随机变量的历史和现状，因此所谓随机变量基本性态的维持不变也就是要求样本数据时间序列的本质特征仍能延续到未来。我们用样本时间序列的均值、方差、协（自）方差来刻画该样本时间序列的本质特征。于是，我们称这些统计量的取值在未来仍能保持不变的样本时间序列具有平稳性。可见，一个平稳的时间序列指的是：遥想未来所能获得的样本时间序列，我们能断定其均值、方差、协方差必定与眼下已获得的样本时间序列等同。是什么意思？

Sample time series show the history and current status of the random variable, the so-called random variables state remains unchanged is to ask the essential characteristics of the sample data time series can still continue into the future. Sample time series of the mean, variance, co-(self-) varian

Sample time series show a random variable's history and current situation and the so-called basic random variables of the same mentality that is also called sample data time-series of the essential features are still able to continue into the future. We have a sample of the time series average of th

Sample time series showing the history and present situation of random variables, therefore the so-called random%