變量數(shù)列中，各組頻率之和應(yīng)（）

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 （）.

Which of the following statements is not true？（）

某企業(yè)的生產(chǎn)計劃完成百分比采用如下分組，請指出哪項是正確的（）

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

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？

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？（）

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

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 （）.