Chapter 4

Chapter 4 - Chapter 4 Sample Surveys In The Real World...

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Chapter 4 Sample Surveys In The Real World

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Outline Sampling Errors Random and Non-Random Non-sampling Errors Wording Question Living With Non-sampling Errors The Real World (not the tv show)
Motivation Example Ex. 42% Americans believe immigration policy needs reform 95% M.O.E. = 3.2% Question: Do you think its safe to infer about the population here. Simple Random Sample? Not so simple Not so random Never Answered Phone 938 Answered but wouldn’t talk 678 Not eligible: < 18 or language barrier 221 Incomplete interview 42 Complete Interview 1000 Total Called 2879

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Definitions Recall for inference to be made about a population we need a simple random sample. SRS – Each person in population is as likely to be chosen for the sample as the next. Random Sampling error is a specific type of sampling error. It is natural unavoidable error due to the variation of a population. Accounted for in M.O.E. Non-random Sampling Errors are errors caused by the sampling method Cause results to differ from results of a census (population) – sampling technique is bad. Not accounted for in M.O.E. Non-sampling Errors are errors not related to sampling method. Errors as a result of “measurement” technique. Not accounted for in M.O.E.
Sampling Errors

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Two Types of Sampling Error A sampling error occurs when the method in which those individuals from the population are chosen to be in your sample causes the sample to differ from the population. Random sampling error – does not cause bias Non random sampling error – causes bias
Random sampling error occurs no matter how the sample is taken Even if it is a simple random sample

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This note was uploaded on 06/15/2011 for the course STAT 110 taught by Professor Johnson during the Fall '07 term at South Carolina.

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Chapter 4 - Chapter 4 Sample Surveys In The Real World...

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