3-Chapter 5&6 - Edited by Foxit Reader Copyright(C)...

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10/4/2009 1 Data Collection and Sampling Chapter 5 5.1 Methods of Collecting Data • The reliability and accuracy of the data affect the validity of the results of a statistical analysis. • The reliability and accuracy of the data depend on the method of collection. • Three of the most popular sources of statistical data are: – Published data – Observational studies – Experimental studies – This is often a preferred source of data due to low cost and convenience. – Published data is found as printed material, tapes, disks, and on the Internet. For example: Data published by the Stats Canada Published Data – Data published by the organization that has collected it is called PRIMARY DATA. – Data published by an organization different than the organization that has collected it is called SECONDARY DATA . For example: •The Statistical abstracts of Canada, compiles data from primary sources
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10/4/2009 2 Observational study is one in which measurements representing a variable of interest are observed and recorded without controlling any factor that migh • When published data is unavailable, one needs to conduct a study to generate the data. Observational and experimental studies recorded, without controlling any factor that might influence their values. Experimental study is one in which measurements representing a variable of interest are observed and recorded, while controlling factors that might influence their values. • Surveys solicit information from people. • Surveys can be made by means of – personal interview – telephone interview Surveys – self-administered questionnaire A good questionnaire must be well designed: • Keep the questionnaire as short as possible. • Ask short,simple, and clearly worded questions. • Start with demographic questions to help respondents get started comfortably Surveys respondents get started comfortably. • Use dichotomous and multiple choice questions. • Use open-ended questions cautiously. • Avoid using leading-questions. • Pretest a questionnaire on a small number of people. • Think about the way you intend to use the collected data when preparing the questionnaire.
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10/4/2009 3 5.2 Sampling • Motivation for conducting a sampling procedure: –Cos ts . – Population size. – The possible destructive nature of the sampling process. The sampled populatio and the target populatio • The sampled population and the target population should be similar to one another. 5.3 Sampling Plans • We introduce three different sampling plans – Simple random sampling – Stratified random sampling – Cluster sampling Simple Random Sampling • In simple random sampling all the samples with the same size are equally likely to be chosen.
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This note was uploaded on 10/14/2010 for the course ADMS adms 3333 taught by Professor Adms during the Spring '10 term at York University.

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3-Chapter 5&6 - Edited by Foxit Reader Copyright(C)...

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