A summary measure that is computed from a sample to describe a characteristic of the population is called（）

為什么在計算平均指標的基礎上還有必要進一步計算變異指標？

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？（）

在組距數(shù)列中，下限就是（）

最能反映離散程度的指標是（）

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

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

The number of class intervals in a frequency distribution is usually between （）.

對某班級學生的生活狀況進行統(tǒng)計調查，下列標志中屬于不變標志的是（）

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