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？（）

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

如果居民按報(bào)告期價(jià)格購(gòu)買商品需多支出40萬元，報(bào)告期商品銷售額為200萬元，則價(jià)格指數(shù)為（）

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？（）

品合格率指標(biāo)是（）

Simon Arnett, Director of Human Resources, is exploring the causes of employee absenteeism at Buderim Bottling during the last operating year (1 January 2005 to 31 December 2005). Personnel records of 50 employees are selected for analysis. (The plant employs 250.) For this study, the average number days absent for these 50 employees is a （）.

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

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

A student achieves an 82 on the first test in a statistics course. From this, she assumes that her average at the end of the semester (after other tests) will be about 82. This is an example of （）.

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（）