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

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

Which of the following is not the goal of descriptive statistics?（）

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)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（）

A cumulative frequency distribution would provide（）.

Descriptive statistics deals with methods of（）

Which of the following statements is not true？（）

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？

常用的長期趨勢測定的方法有哪些？各有什么特點(diǎn)？