One rule that must always be followed in constructing frequency distributions is that （）.

一個地區(qū)一定時期的商品零售額屬于（）

要了解某地區(qū)全部大學生的就業(yè)情況，那么（）

If the individual class frequency is divided by the total frequency, the result is the （）.

什么是季節(jié)變動？研究它的意義何在？如何測定季節(jié)變動？

If data are grouped into intervals and the number of items in each group is listed, this could be called a （）

Which of the following is not the goal of descriptive statistics?（）

時間序列構成因素有哪些？分解的基本原理和思路是什么？

Simon Arnett, Director of Human Resources, is exploring the causes of employee absenteeism at Buderim Bottling during the last operating year (1 January 2005 to 31 December 2005). Personnel records of 50 employees are selected for analysis. (The plant employs 250.) For this study, the average number days absent for these 50 employees is a （）.

Descriptive statistics deals with methods of（）