1、类别类别简单随机抽样简单随机抽样系统抽样系统抽样分层抽样分层抽样各自各自特点特点从总体中逐个从总体中逐个抽取抽取将总体均分成几个部将总体均分成几个部分，按事先确定的规分，按事先确定的规则在各部分抽取则在各部分抽取将总体分成几层，将总体分成几层，分层进行抽取分层进行抽取相互相互联系联系在起始部分采用简单在起始部分采用简单随机抽样随机抽样在各层抽样时采用在各层抽样时采用简单随机抽样或系简单随机抽样或系统抽样统抽样适用适用范围范围总体中的个体总体中的个体数较少数较少总体中的个体数较多总体中的个体数较多总体由存在明显差总体由存在明显差异的几部分组成异的几部分组成共同共同点点抽样过程中每个个体被抽到的可
2、能性相等；抽样过程中每个个体被抽到的可能性相等；每次抽出个体后不再放回，即不放回抽样每次抽出个体后不再放回，即不放回抽样支持支持A方案方案支持支持B方案方案支持支持C方案方案35岁以下的人数岁以下的人数20040080035岁以上岁以上(含含35岁岁)的人数的人数100100400(单击进入电子文档单击进入电子文档)团Tiffany，a 16yearold girl，was very shy.Last September，her best frien“I was really sad the moment I heard the bad news and I didnt know what t
3、o do，”Tiffany recalled.“I shut myself in my room for a whole week.It was then that my aunt took me to a sports club one Saturday and I saw so many young people playing different kinds of sports there.I signed up for a beginners course in volleyball and since then I have been playing this sport.Now I
4、 practice twice a week there.It is wonderful playing sports in this club and I have made lots of friends as well.2 ”The most basic aim of playing sports is that you can improve your health even if you are not very good at sports.Besides，you can get to know a circle of people at your age while playin
5、g sports.3 Since she joined the sports club，s I got used to the life here.And now I know lots of(5)_ here.For example,when I meet my friend on the street,I usually(6)_ him like this,“Hey,where are you going?”In our country if someone asks this,people may get(7)_ but in this country people wont.Of co
6、urse,there are some other interesting things here.Ill tell you about them next time.he has opened up herself and now she has become very active and enjoys meeting and talking with others.1Its polite for girls to kiss each other on the side of the face.s also become more confident.团圆圆一家在台湾可受欢迎了。每天，小朋友们排着长队，等着跟它们合影留念。从“排着长队”体现出每天喜欢它们的人不计其数，特别受选D.A.根据同类项合并法则,与不是同类项,不能合并,故本选项错误;B.根据算术平方根的定义,=3,故本选项错误;C.根据同底数幂的乘法aa2=a3,故本选项错误;D.根据积的乘方,(2a3)2=4a6,故本选项正确.欢迎。从“合影留念”体现出大家都想和大熊猫留住最美丽的瞬间以作纪念。Nothing can be accomplished without norms or standards.精品资料！感谢阅读下载！
