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# lecture12 - Chapter 7–one sample inference I Confidence...

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Unformatted text preview: Chapter 7–one sample inference I Confidence interval for population mean I The idea is to give an interval such that you can claim with certain probability, the true population parameter is going to be in the interval. I In the large sample case, ¯ x ± 2 σ ¯ x = ¯ x ± 2 σ √ n has good coverage probabilities. Why? Hospital patients I For this dataset, we can read from the book (page 307) that ¯ x = 4 . 53 days and s = 3 . 68 days. So we can construct the interval ¯ x ± 2 σ ¯ x = 4 . 53 ± 2 σ √ 100 , but we don’t know σ , how can we approximate it? ¯ x ± 2 σ √ 100 ≈ ¯ x ± 2 s √ 100 = 4 . 53 ± 2 3 . 68 10 = 4 . 53 ± . 74 . Interval estimator and confidence coefficient I Definition 7.2: An interval estimator or ( confidence interval) is a formula that tells us how to use sample data to calculate an interval that estimates a population parameter. I Definition 7.3: The confidence coefficient is the probability that an interval estimator encloses the population parameter – that is, the relative frequency...
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## This note was uploaded on 06/06/2011 for the course STAT 515 taught by Professor Zhao during the Spring '10 term at South Carolina.

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lecture12 - Chapter 7–one sample inference I Confidence...

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