中文摘要：

本文从条件期望的抽象定义出发给出一类条件期望的计算方法．作为应用，作者计算了文中求条件期望的两个例子．经过比较发现，本文的方法要简单些．

英文摘要：

In this note, we provide a method of finding conditional expectations based on its definition. As applications, two examples are provided, for which our method is simpler than that of Brzezniak-Zastawniak.