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

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

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

在组距数列中，下限就是（）

什么是季节变动？研究它的意义何在？如何测定季节变动？

以2000年a0为最初水平，2016年an为最末水平，计算钢产量的年平均发展速度时，须开（）

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 （）.

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？（）

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 （）.