“在统计学上，‘平均值’和‘平均数’是相同的。但我们的课本并不是这样的解释。”
As a statistician, I think it is very necessary to point this out: in statistics, average and mean are different. an average can be thought as sample mean, but this does not mean the meaning of average is the same as the meaning of mean. Theoretical speaking, mean is referred as the true estimate of an expected value of underlying random variable, which is often estimated by sample mean. So, average is only a sample estimate of mean, but not the true value. The different between the estimate and the true value is often called a bias. To some extend, the textbook is right in this sense.
SFU数学教授：加国数学课本错误百出