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？（）

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

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

在組距數(shù)列中，下限就是（）

最能反映離散程度的指標(biāo)是（）

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（）

對(duì)全國(guó)各鐵路交通樞紐的貨運(yùn)量、貨物種類(lèi)等進(jìn)行調(diào)查，以了解全國(guó)鐵路貨運(yùn)概況。這種調(diào)查屬于（）

A cumulative frequency polygon is also called （）.

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

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