对全国各铁路交通枢纽的货运量、货物种类等进行调查，以了解全国铁路货运概况。这种调查属于（）

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 （）.

A cumulative frequency distribution would provide（）.

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

The number of phone calls arriving at a switchboard each hour has been recorded and the following frequency distribution has been developed.What is the cumulative frequency of the third class？（）

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

一个地区一定时期的商品零售额属于（）

要了解某地区全部大学生的就业情况，那么（）

Claudia Taylor, Director of Global Industrial Sales in Melbourne, is concerned by a deteriorating sales trend. Specifically, the number of customers is stable at 1500 but they are purchasing less each year. She orders her staff to search for causes of the downward trend by selecting a focus group of 40 industrial customers. For this study, the set of 40 industrial customers is a （）.

最能反映离散程度的指标是（）