问题如下：
If analyst collect a random sample of 100 students in school with 1000 students, and we found the sample mean heights under 1.7 centimeters, but the population mean heights is 1.8 centimeters. A friend has asked you to explain the differences between sample mean and population mean. Which of the following will you most likely include in your explanation?
选项：
A. because of sampling error
B. because of sampling distribution
C. because of systematic sampling
解释：
A is correct, because any difference between the sample mean and the population mean is called sampling error.
老师，请问这个知识点是在哪里讲的？没有印象
