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？（）

Which of the following statements is not true？（）

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). The average number of absences per employee, calculated from the personnel data of all employees, is a （）.

常用的长期趋势测定的方法有哪些？各有什么特点？

最能反映离散程度的指标是（）

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

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

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（）

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 （）.

某厂某年职工劳动生产率为20000元，是历史最高水平的1.2倍。这里的1.2倍是（）