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

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（）

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 （）.

Descriptive statistics deals with methods of（）

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（）

常用的長期趨勢測定的方法有哪些？各有什么特點？

If data are grouped into intervals and the number of items in each group is listed, this could be called a （）

企業(yè)生產(chǎn)一種產(chǎn)品需順次經(jīng)過四個車間，這四個車間的廢品率分別為1.5%、2.0%、2.0%和1.0%。該企業(yè)生產(chǎn)這種產(chǎn)品的平均廢品率是多少？

A cumulative frequency polygon is also called （）.

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？