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 （）.

A summary measure that is computed from a sample to describe a characteristic of the population is called（）

在组距数列中，下限就是（）

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 （）.

最能反映离散程度的指标是（）

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 （）.

一个地区一定时期的商品零售额属于（）

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

常用的长期趋势测定的方法有哪些？各有什么特点？

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