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（）

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？（）

為什么在計算平均指標的基礎(chǔ)上還有必要進一步計算變異指標？

什么是季節(jié)變動？研究它的意義何在？如何測定季節(jié)變動？

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？

一個地區(qū)一定時期的商品零售額屬于（）

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

If data are grouped into intervals and the number of items in each group is listed, this could be called a （）

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 cumulative frequency of the third class？（）

Which of the following statements is not true？（）