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（）

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

變量數(shù)列中，各組頻率之和應(yīng)（）

The number of class intervals in a frequency distribution is usually between （）.

常用的長(zhǎng)期趨勢(shì)測(cè)定的方法有哪些？各有什么特點(diǎn)？

在組距數(shù)列中，下限就是（）

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？（）

最能反映離散程度的指標(biāo)是（）

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 （）.