Chapter3.12 - 3. Producing Data Introduction Chapters 1 and...

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3. Producing Data Introduction Chapters 1 and 2 describe methods for exploring data. Such exploratory data analysis is used to determine what the data tell us about the variables measured and their relations to each other. Conclusions apply to the data observed and may not generalize beyond these data. Statistical inference produces answers to specific questions, along with a statement of how confident we are that the answer is correct. Answers are usually intended to apply beyond the data observed. This requires careful production of data appropriate for answering the specific questions asked. 3.1 First Steps Good, high quality data is the key to making good inferences, and learning about a problem. This chapter presents some concepts that will help you recognize good data production systems.
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Anecdotal data based on a few isolated cases is usually unreliable. Available data collected for other purposes, such as data produced by government agencies(for example, U.S. Census Bureau http://www.census.gov/ ), can be helpful but again is not always reliable. Sampling selects a part of population of interest to represent the whole. Sample Population Take Sample Inference Done properly, sampling can yield reliable information about a population. Two basic types of studies are observational studies and designed experiments . An observational study observes individuals and measures variables of interest and does not
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attempt to influence the responses. A sample survey is a type of observational study . A designed experiment deliberately imposes some treatment or conditions on individuals to observe their responses. A drug study were some patients get drug A and others get drug B is an example of an experiment. The study investigator imposes which subjects get which
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This document was uploaded on 02/07/2012.

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Chapter3.12 - 3. Producing Data Introduction Chapters 1 and...

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