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Unformatted text preview: Chapter 5: Sampling * What is a sample &amp; why would we want to use one? Generalizability or External Validity Population - Sample- Basic Sampling Types * Probability sampling * Known probability of selection into sample * Non-probability sampling * Unknown probability of selection into sample Sampling Methods * Probability Sampling Methods * Sampling methods that allow us to know in advance * Allows researchers to select study subjects * Even when a random selection process is used, two common problems can result in bias * (1) Incomplete sampling frame * (2) Nonresponse * Even IF sampling frame and response rate are good, there is still error associated with every probability sample taken. * Important kinds of probability samples Simple Random Sample * Identifies cases strictly on the basis of chance How to obtain a Simple Random Sample (SRS) * Assign a number to all the elements listed in the sampling frame. 1- John 11- Tina 21- Ronald 2- Kelli 12- John 22- Dave 3- Joan 13- Bobby 23- Taylor 4- Stephen 14- Jeff 24- Ashley 5- Sharon 15- Katie 25- Thomas N= 30 students 6- Robert 16- Mike 26- Jack n = 6 students (20% sample) 7- Mark 17- Megan...
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- Spring '08
- representative, incomplete sampling frame