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Sampling 抽樣 中央大學. 資訊管理系 范錚強 mailto: 2015.04 updated 11.

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Presentation on theme: "Sampling 抽樣 中央大學. 資訊管理系 范錚強 mailto: 2015.04 updated 11."— Presentation transcript:

1 Sampling 抽樣 中央大學. 資訊管理系 范錚強 mailto: 2015.04 updated 11

2 中央資管:范錚強 2 The Nature of Sampling Sampling Population Element Population Census Sampling frame

3 中央資管:范錚強 3 Why Sample? Greater accuracy Availability of elements Availability of elements Greater speed Sampling provides Sampling provides Lower cost

4 中央資管:范錚強 4 When Is a Census Appropriate? NecessaryFeasible

5 中央資管:范錚強 5 What Is a Valid Sample? Accurate Precise _  和 x 的差異 沒有偏誤

6 中央資管:范錚強 6 目標母體 外部效度 External Validity 正式描述 規劃樣本 實際達成的母體 實際達成 的樣本

7 中央資管:范錚強 7 Types of Sampling Designs Element Selection ProbabilityNonprobability UnrestrictedSimple random Convenience 便利 RestrictedComplex random Purposive 立意 SystematicJudgment ClusterQuota Stratified Snowball Double

8 中央資管:范錚強 8 Steps in Sampling Design What is the target population? What are the parameters of interest? What is the sampling frame? What is the appropriate sampling method? What size sample is needed?

9 中央資管:范錚強 9 When to Use Larger Sample Sizes? Desired precision Number of subgroups Number of subgroups Confidence level Population variance Small error range

10 中央資管:范錚強 10 Simple Random Advantages Easy to implement with random dialing Disadvantages Requires list of population elements Time consuming Uses larger sample sizes Produces larger errors High cost

11 中央資管:范錚強 11 Systematic Advantages Simple to design Easier than simple random Easy to determine sampling distribution of mean or proportion Disadvantages Periodicity within population may skew sample and results Trends in list may bias results Moderate cost

12 中央資管:范錚強 12 Stratified Advantages Control of sample size in strata Increased statistical efficiency Provides data to represent and analyze subgroups Enables use of different methods in strata Disadvantages Increased error will result if subgroups are selected at different rates Especially expensive if strata on population must be created High cost

13 中央資管:范錚強 13 Cluster Advantages Provides an unbiased estimate of population parameters if properly done Economically more efficient than simple random Lowest cost per sample Easy to do without list Disadvantages Often lower statistical efficiency due to subgroups being homogeneous rather than heterogeneous Moderate cost

14 中央資管:范錚強 14 Stratified and Cluster Sampling Stratified Population divided into few subgroups Homogeneity within subgroups Heterogeneity between subgroups Choice of elements from within each subgroup Cluster Population divided into many subgroups Heterogeneity within subgroups Homogeneity between subgroups Random choice of subgroups

15 中央資管:范錚強 15 Nonprobability Samples Cost Feasibility Time No need to generalize Limited objectives

16 中央資管:范錚強 16 Nonprobability Sampling Methods Convenience Judgment Quota Snowball

17 中央資管:范錚強 17 特殊的設計考量 你的對象 個人? 企業? 企業裡的個人 誰? 是否能代表企業?

18 中央資管:范錚強 18 複雜的設計 有一些構念是企業(團對、組織 … ) 有一些構念是個人 甚至是不同的個人 Matching 事後配對 發給 CEO 和 CIO ,針對回卷比對 事前配對 設計時就想好如何搭配

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