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？（）

什么是季節(jié)變動(dòng)？研究它的意義何在？如何測(cè)定季節(jié)變動(dòng)？

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（）

最能反映離散程度的指標(biāo)是（）

A cumulative frequency distribution would provide（）.

A cumulative frequency polygon is also called （）.

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 （）.

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

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

企業(yè)生產(chǎn)一種產(chǎn)品需順次經(jīng)過四個(gè)車間，這四個(gè)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？