某廠某年職工勞動生產率為20000元，是歷史最高水平的1.2倍。這里的1.2倍是（）

某企業(yè)的生產計劃完成百分比采用如下分組，請指出哪項是正確的（）

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 （）.

Descriptive statistics deals with methods of（）

為什么在計算平均指標的基礎上還有必要進一步計算變異指標？