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

對全國各鐵路交通樞紐的貨運量、貨物種類等進行調查，以了解全國鐵路貨運概況。這種調查屬于（）

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 approximate range of the number of phone calls arriving each hour？（）

A cumulative frequency polygon is also called （）.

為什么在計算平均指標的基礎上還有必要進一步計算變異指標？

A student achieves an 82 on the first test in a statistics course. From this, she assumes that her average at the end of the semester (after other tests) will be about 82. This is an example of （）.

One advantage of a stem and leaf plot over a frequency distribution is that （）.

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

要了解某地區(qū)全部大學生的就業(yè)情況，那么（）

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 （）.