Chapter 4 - Chapter 4 Sample Surveys in the Real World In...

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Chapter 4 Sample Surveys in the Real World In this chapter Types of error Survey questions Believing a statistic Types of error Sampling frame – list of every individual in the population Under-coverage – when some groups in the population are left out of the sample Example Suppose your population is all Lexington residents and you are going to conduct phone surveys. A list of all residents in Lexington would be your sampling frame. If you use a phone book to make the calls this would be under-coverage. Obviously, everyone does not have a phone. Sampling errors – Errors that result from sampling Random sampling error – This is the error we that comes from us taking a sample we expect this error and can calculate it. Margin of error covers only random sampling error. (other sources of error can cause large bias) Bad sampling methods – Any deviation from a random sample is a bad sampling method which causes bias and increases the error in our estimate. Non-sampling errors – Errors that do not result from sampling Processing error – Any data entry or arithmetic mistake. Response error – Incorrect response from subject either intentionally or just because no effort was given when taking the survey. Non-response – This is the biggest problem with surveys. If you send out 1000 surveys, you will not typically get 1000 back.
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Example If you send out 3200 surveys and you only get back 1200, then you have a problem. When setting up a study we make sure the sample is representative of the population.
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Chapter 4 - Chapter 4 Sample Surveys in the Real World In...

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