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 （）.

某企業(yè)的生產(chǎn)計(jì)劃完成百分比采用如下分組，請指出哪項(xiàng)是正確的（）

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

A cumulative frequency polygon is also called （）.

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？（）

對某班級學(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（）

Which of the following statements is not true？（）

企業(yè)生產(chǎn)一種產(chǎn)品需順次經(jīng)過四個車間，這四個車間的廢品率分別為1.5%、2.0%、2.0%和1.0%。該企業(yè)生產(chǎn)這種產(chǎn)品的平均廢品率是多少？

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（）

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 （）.