Section outline

  • General

    Collapse all Expand all

  • 实施随机抽样

    Implementing Random Sampling 
    ::实施随机抽样

    Obtaining a true random sample is more complex that most people think, but there are a number of viable ways to build a random sample from different types of populations.  In general, the first and most important step is to organize the identities of your population into a set that can be numbered, since numbers are relatively easy to randomize.
    ::获得真正的随机抽样对大多数人来说更为复杂,但有多种可行的方法可以建立来自不同类型人口的随机抽样。 一般来说,最重要的第一步是将你人口的身份组织成一组可以编号的样本,因为数字比较容易随机化。

    Once each member of your population is assigned to a unique numeric identifier, there are a few ways to choose your actual sample :
    ::一旦贵国人口的每一成员被分配到一个独特的数字标识符,就有几种选择实际样本的方法:

    • Simple Random Sample :  Use a random number generator or a random number table to identify the members of your sample directly from your list.  If you get a number from the random source that does not directly correspond to one on your list, pick another until you do.  Continue the process until you have enough members of your sample.  (Example A)
      ::简单随机抽样 : 使用随机数字生成器或随机数字表直接从列表中识别样本成员。 如果您从随机来源获得与列表中不直接对应的号码, 请选择另一个数字直到您找到。 继续此进程, 直到您有足够的样本成员 。 (例 A)
    • Systematic Random Sampling :  First divide the total number of members in the population to be sampled by the number of members you want in your sample.  The result is your step size.  Use a random generator to identify a starting number, then skip down from the starting number by your step size and pick the result, skip down again and pick, until you get as many results as you need for your sample.  (Example B)
      ::系统随机抽样 : 首先将要抽样的人群中的成员总数除以在样本中要抽样的成员数目。 结果就是您的步数大小 。 使用随机生成器来识别起始数, 然后用步数跳过起始数, 然后选择结果, 跳过并选择结果, 跳过并选择结果, 直到您获得样本所需的结果数量 。 (例B)
    • Stratified Random Sampling :  This method is most effective when sampling a population with a limited number of disparate sub-groups formed by members’ shared attributes or characteristics.  Start by dividing the population into the recognized subgroups , and then use the simple random sampling method above to either:
      • Pick the same percentage of your sample as each subgroup represents of the population (proportional random sampling).  This method ensures that the sample space will have the same proportion of each subgroup as the population. OR
        ::选取与每个分组代表人口(比例随机抽样)相同比例的样本。这种方法确保每个分组的样本空间与人口具有相同比例。 OR
      • Pick an equal number of units from each subgroup until you fill your sample space (disproportionate stratified random sampling).  This method may be used particularly if one or more subgroups are too small to result in a useable sample when the proportional method is used.  To yield accurate results, you will need to apply proper weighting to your results.
        ::从每个分组中选择相同数量的单位,直到您填充样本空间( 不成比例的分层随机抽样) 。 特别是如果一个或一个以上分组太小, 无法在使用比例法时得出可用的样本, 这种方法可能会被使用。 要得出准确的结果, 您需要对结果进行适当加权 。

      ::分层随机抽样: 在用成员共有属性或特性组成的不同分组数量有限的人口进行抽样时,这一方法最为有效。 从将人口分为公认的分组开始,然后使用上面的简单随机抽样方法: 选择与每个分组代表人口相同的样本比例( 比例随机抽样) 。 这种方法确保每个分组的样本空间与人群的比例相同。 或从每个分组中选择相同数量的单位, 直到您填满样本空间( 比例偏小的随机抽样 ) 。 特别是如果一个或多个分组太小, 无法在使用比例方法时产生可用样本, 这种方法可能会被使用。 要得出准确的结果, 您需要对结果进行适当的加权 。
    • (multistage): This method is most applicable to very large populations spread over large geographic areas.   For instance, if you wanted to sample individual classrooms randomly sampled from the entire Midwest United States, you might first collect a random sample of states in the area, then a random sample of districts from each sampled state, then a random sample of schools from each sampled district, and finally a random sample of classrooms(s) from each sampled school.  It is important to use a random sampling method at each stage.
      :sad多阶段):这种方法最适用于分布在大地理区域的众多人口。例如,如果你想抽取来自整个中美州随机抽样的个别教室,你可能首先收集该地区的随机州抽样,然后抽取每个抽样州的地区抽样,然后抽取每个抽样地区学校的随机抽样,最后抽取每个抽样学校的教室抽样。重要的是在每个阶段使用随机抽样方法。

    Implementing Simple Random Samples 
    ::实施简单随机抽样

    How would a simple random sample be implemented in the following situation?
    ::如何在以下情况下实施简单的随机抽样?

    Ciere wants to collect a random sample of 25 students out of the 146 members of the Junior Class at school.
    ::Ciere想收集学校146名初中学生中25名学生的随机抽样。

    To collect a simple random sample , Ciere should assign a unique number to each student in the class and use a random number generator to pick 25 numbers between 1 and 146.  Each student associated with one of the chosen numbers becomes part of the sample.
    ::为了收集简单的随机抽样,Ciere应为该班每个学生指定一个独有的号码,并使用随机数字生成器在1至146之间取出25个数字。每个与所选数字之一相关的学生都成为样本的一部分。

    Systematic Random Sampling 
    ::系统随机抽样

    Howard wants to collect a sample of 15 dogs from the local animal shelter for his study on most commonly surrendered dog breeds.  If he decides to use a systematic random sample, what would the process be?
    ::霍华德想从当地动物收容所收集15只狗的样本,以研究最常见的上传狗品种。 如果他决定使用系统的随机样本,过程会是什么?

    lesson content

    Howard should obtain a list of all the dogs in the shelter from the front office.  He should identify the number of dogs, and assign a unique number to each one. He should next divide the total number of dogs in the shelter by 15 (the number he wants in his final sample) to get n (the step size).  Finally, he should roll a couple of dice and start by counting down from the top of the numbered list of dogs until he reaches the number he rolled.  From that point, he should take every  n t h dog until he reaches 15 dogs.
    ::霍华德应该从前台获得避难所内所有狗的名单。 他应该确定狗的数量, 并给每个狗指定一个独特的号码。 他接下来应该将庇护所内狗的总数除以15 (他在最后抽样中想要的) 。 最后, 他应该滚动几个骰子, 开始从编号的狗名单的顶部开始计数, 直到他达到他所滚动的狗数量。 从这一点开始, 他应该把每只N型狗都带走, 直到他达到15只狗。

    Arranging Random Sampling 
    ::排列随机抽样

    Erina is considering the possibility of opening a small sporting goods store just down the street from the local WalMart.  Her calculations suggest that if at least 13% of the estimated 4000 adult customers visiting WalMart each day spend money on sporting goods, then her store has a good chance of being profitable based on providing those customers an alternative.  Erina plans to use the graph below to help determine the sample size she will need.  How might she arrange a random sampling of the customers to get the data for her survey ?
    ::她的计算表明,如果估计每天访问沃尔玛的4 000名成年顾客中至少有13%的人花在体育用品上,那么她的商店就很有可能在为这些顾客提供替代产品的基础上获得利润。

    lesson content

    This is another good situation for a systematic random sampling.  Erina’s population in this case is expected to be approximately 4000, which is the estimated daily number of customers at her WalMart.  We can estimate based on the graph that for a population of 4,000, she will need a sample of 350 people.
    ::这是进行系统性随机抽样的另一个好情况。 在本案中,埃丽娜的人口预计约为4000人,即她的沃尔玛每天估计的客户人数。 我们可以根据图数估算,对于4000人来说,她需要350人的抽样。

    To find the step size "> ( n ) , we divide: 4000 350 ≈ 11
    ::为了找到步数大小No,我们划分:4000350*11。

    Erina should roll a pair of dice, let that number of people go by, then question every  11 t h person out the door to see if they purchased sporting goods.
    ::Erina应该滚一对骰子, 让这个数量的人经过, 然后问出第11个人 门外看看他们是否购买了运动用品。

    To increase the accuracy of her predictions, Erina should repeat the process on different days of the week, and ideally in different seasons (which might not be reasonable depending on her time frame), to see how the purchase types cycle.
    ::为了提高预测的准确性,Erina应在每周的不同日子里重复这一过程,最好在不同的季节(这可能不合理,取决于她的时间框架)这样做,以便了解采购类型周期如何。

    Earlier Problem Revisited 
    ::重审先前的问题

    If you were given a list of student names or addresses, could you build a random sample from it?
    ::如果你有学生姓名或住址的名单, 你能从中建立随机样本吗?

    Having worked through this lesson, you probably know that there are a number of ways to build a good, random sample.  Likely the most efficient option since you already have a list would be either a simple random or systematic random sample.
    ::通过这个课程,你可能知道有很多方法可以构建一个好的随机样本。 可能因为你已经有了一个列表,所以最有效的选择就是简单随机或者系统随机样本。

    Examples 
    ::实例

    Which random sampling technique (Simple, Systematic, Cluster, Multi-Stage, or Stratified) would be most appropriate in each of the following situations?
    ::哪些随机抽样技术(简单、系统、组群、多级或分级)最适于下列每一种情况?

    Example 1
    ::例1

    Finding the ratio of girls vs. boys in a high school with 400 students.
    ::在有400名学生的中学中,发现女生与男生的比例。

    A simple random sample would work here. Number the students 1 - 400 and use a random number generator to find 50 or so students for your sample.
    ::简单随机的样本可以在这里工作。 学生人数为 1 - 400, 并使用随机数字生成器为样本找到大约 50 个学生 。

    Example 2
    ::例2

    Identifying the favorite soda of students at a football game.
    ::确定足球赛中学生们最喜爱的苏打水

    Students often like to drink the same as their friends, so a cluster sample of 2 or 3 students from each of several groups of students would be a good method. Don't forget to use a random number generator to choose the groups and members of each group. 
    ::学生通常喜欢和朋友一样喝酒,因此,由来自不同学生组的2或3名学生进行分组抽样调查是一个很好的方法。 不要忘了使用随机数字生成器来选择每个群体的群体和成员。

    Example 3
    ::例3

    The preferred biscuit of each of the different dog breeds at a Humane Society.
    ::每个不同的狗种的首选饼干 在一个人道协会。

    Since you want to specifically evaluate the favorite biscuit of each breed, you should do a stratified sample. Identify the number of breeds, and the number of dogs of each, then use a random method of choosing a number of representatives of each breed. 
    ::由于您想要具体评估每种品种的最爱饼干, 您应该做一个分层样本。 确定每种品种的数量和狗的数量, 然后使用随机方法选择每种品种的代表数 。

    Example 4
    ::例4

    The average ACT or SAT score of 500 students from rural schools in the State of Colorado.
    ::科罗拉多州农村学校500名学生的平均青蒿素综合疗法或SAT分数为500人。

    This would be a multi-stage sample.  First you need to select only students from rural schools from the entire population of CO students (perhaps by randomly selecting a limited number of rural schools).  Second, you should number the subset of students individually and divide the total by 500 to obtain your ‘step size’ n .  Third, use a random generator to select a starting number and choose every n t h student until you reach 500.
    ::这将是一个多阶段抽样。 首先,你需要从全部CO学生中只从农村学校中挑选学生(也许通过随机选择数量有限的农村学校)。 其次,你应该将学生的子集逐个编号,并将学生总数除以500,以获得你的“步数”n。 第三,使用随机生成器来选择一个起始数,并选择每个N学生,直到你达到500。

    Review 
    ::回顾

    Identify appropriate sampling methods to collect samples in the following situations:
    ::确定在以下情况下收集样品的适当取样方法:

    1. Identifying the contents of an opaque bag.
      ::识别一个不透明的袋子的内容。
    2. Estimating the percentage of shoppers who use plastic bags at a specific store.
      ::估计在特定商店使用塑料袋的购物者的百分比。
    3. Estimating the percentage of students in your school who like vampire movies.
      ::估计你学校里 喜欢吸血鬼电影的学生的比例
    4. Estimating the percentage of dogs that bark at guests and passing cars.
      ::估计狗对客人和过路车叫狗的百分比
    5. Predicting the most popular book genre among students in your class.
      ::预测班级学生中最流行的书籍流派。
    6. Predicting the most popular book genre among U.S. elementary school students.
      ::预测美国小学生中最流行的图书流派。
    7. Estimating the percentage of defective incandescent bulbs produced at a factory.
      ::估计工厂生产的有缺陷的白炽灯泡的百分比。
    8. Estimating the percentage of defective light bulbs produced at a factory.
      ::估计工厂生产的有缺陷的灯泡的百分比。
    9. Estimating the percentage of defective incandescent bulbs produced at U.S. factories.
      ::估计美国工厂生产的有缺陷白炽灯泡的百分比。
    10. Estimating the percentage of teachers at a school that work more than two Saturdays per month.
      ::估计每月工作两个星期六以上的学校教师的百分比。

    Review (Answers)
    ::回顾(答复)

    To see the answer key for this book, go to the and click on the Answer Key under the ' ' option.
    ::要查看本书的答案键, 请在“ ” 选项下点击答案键 。