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？（）

最能反映離散程度的指標是（）

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？

某企業(yè)2018年技術(shù)工占50%，2019年新招收了一批學徒工，使學徒工的比重增加了10%。假定全廠各級工資水平均無變化，則2019年職工總平均工資將（）

如果居民按報告期價格購買商品需多支出40萬元，報告期商品銷售額為200萬元，則價格指數(shù)為（）

變量數(shù)列中，各組頻率之和應（）

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

常用的長期趨勢測定的方法有哪些？各有什么特點？

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 （）.

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