常用的長期趨勢測定的方法有哪些？各有什么特點？

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

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（）

對全國各鐵路交通樞紐的貨運量、貨物種類等進行調(diào)查，以了解全國鐵路貨運概況。這種調(diào)查屬于（）

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 （）.

Which of the following statements is not true？（）

某班的學(xué)習按考試成績分為60分以下，60-70，70-80，80-90，90-100，這種分組（）

時間序列構(gòu)成因素有哪些？分解的基本原理和思路是什么？

A cumulative frequency polygon is also called （）.

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？（）