203ch14_slides.pdf - STAT 203 Chapter 14 Sampling...

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STAT 203 Chapter 14 Sampling Distribution Models Population vs. sample, parameter vs. statistic Recall that a population contains the entire collection of individuals that one wants to study, and a sample is a subset of individuals selected from a population. A parameter refers to a numerical summary of a population. The counterpart of a sample is a statistic . The value of a parameter is fixed yet unknown in practice. We use statistics to estimate population parameters. Due to sampling variability (variation from sample to sample), a statistic takes on different values for different samples. A statistic is a random variable. Eugenia Yu, UBC Department of Statistics. Not to be copied, used, or revised without explicit written permission from the copyright owner. 1
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STAT 203 Sampling Distribution of Proportions (Percentages) The true proportion of individuals sharing a certain characteristic in a population is the population proportion p (which is a parameter), 0 < p < 1 . For a sample of n individuals randomly selected from the population, the sample proportion (which is a statistic) is given by ˆ p = # individuals sampled who have the characteristic sample size n Eugenia Yu, UBC Department of Statistics. Not to be copied, used, or revised without explicit written permission from the copyright owner. 2
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STAT 203 The value of the population proportion p is fixed but is usually unknown. The sample proportion ˆ p is used to estimate the true population proportion. Due to sampling variation, ˆ p varies across samples, and is unlikely to be exactly equal to p
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  • Winter '18
  • EugeniaHoiYinYu
  • Standard Deviation, Eugenia Yu, UBC Department of Statistics

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