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？（）

一個(gè)地區(qū)一定時(shí)期的商品零售額屬于（）

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

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

什么是季節(jié)變動(dòng)？研究它的意義何在？如何測(cè)定季節(jié)變動(dòng)？

Descriptive statistics deals with methods of（）

要了解某地區(qū)全部大學(xué)生的就業(yè)情況，那么（）

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 （）.

The number of class intervals in a frequency distribution is usually between （）.

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 （）.