Unformatted text preview: The variability of a statistic is described by the spread of its sampling distribution . The spread of is determined by the sampling design and the sample size n. statistics from larger probability samples have smaller spreads . To reduce bias, use random sampling. To reduce variability, use larger sample. Variability of statistics is usually reported by giving a margin of error for conclusions based on sample results. Approval of an institutional review board is required for studies that involve human or animals as subjects. Human subjects must give informed consent if they are to participate in experiments. Data on human subjects must be kept confidential. Multi Rule: if A and B are independent∩ ∪ P(A∩B) = P(A) * P(B) “disjoint” e “ independent” o S j P(A) = P(A∩B) +P(A∩C) B e C o S j...
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 Spring '10
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 stratified random sample, Voluntary Response Samples

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