對某班級學(xué)生的生活狀況進行統(tǒng)計調(diào)查，下列標(biāo)志中屬于不變標(biāo)志的是（）

對全國各鐵路交通樞紐的貨運量、貨物種類等進行調(diào)查，以了解全國鐵路貨運概況。這種調(diào)查屬于（）

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 is not the goal of descriptive statistics?（）

A cumulative frequency polygon is also called （）.

某班的學(xué)習(xí)按考試成績分為60分以下，60-70，70-80，80-90，90-100，這種分組（）

A cumulative frequency distribution would provide（）.

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 （）.

品合格率指標(biāo)是（）

變量數(shù)列中，各組頻率之和應(yīng)（）