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

為什么在計(jì)算平均指標(biāo)的基礎(chǔ)上還有必要進(jìn)一步計(jì)算變異指標(biāo)？

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（）

一個(gè)地區(qū)一定時(shí)期的商品零售額屬于（）

Which of the following is best to show the percentage of a total budget that is spent on each category of items？（）

對(duì)某班級(jí)學(xué)生的生活狀況進(jìn)行統(tǒng)計(jì)調(diào)查，下列標(biāo)志中屬于不變標(biāo)志的是（）

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

要了解某地區(qū)全部大學(xué)生的就業(yè)情況，那么（）

在組距數(shù)列中，下限就是（）

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？（）