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

在组距数列中，下限就是（）

某班的学习按考试成绩分为60分以下，60-70，70-80，80-90，90-100，这种分组（）

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？（）

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 （）.

对某班级学生的生活状况进行统计调查，下列标志中属于不变标志的是（）

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

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 （）.

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

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？（）