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). Personnel records of 50 employees are selected for analysis. (The plant employs 250.) For this study, the average number days absent for these 50 employees is a （）.

對(duì)某班級(jí)學(xué)生的生活狀況進(jìn)行統(tǒng)計(jì)調(diào)查，下列標(biāo)志中屬于不變標(biāo)志的是（）

A cumulative frequency polygon is also called （）.

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

要了解某地區(qū)全部大學(xué)生的就業(yè)情況，那么（）

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？（）

以2000年a0為最初水平，2016年an為最末水平，計(jì)算鋼產(chǎn)量的年平均發(fā)展速度時(shí)，須開（）

某廠某年職工勞動(dòng)生產(chǎn)率為20000元，是歷史最高水平的1.2倍。這里的1.2倍是（）

Descriptive statistics deals with methods of（）

對(duì)全國各鐵路交通樞紐的貨運(yùn)量、貨物種類等進(jìn)行調(diào)查，以了解全國鐵路貨運(yùn)概況。這種調(diào)查屬于（）