One rule that must always be followed in constructing frequency distributions is that （）.

A cumulative frequency polygon is also called （）.

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

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

品合格率指標是（）

要了解某地區(qū)全部大學(xué)生的就業(yè)情況，那么（）

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

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？（）

某企業(yè)2018年技術(shù)工占50%，2019年新招收了一批學(xué)徒工，使學(xué)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（）

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 （）.