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Unformatted text preview: Introduction to inference Estimating with confidence Assignment #8 5.48, 5.50, 5.52, 5.60, 6.18, 6.32, 6.66, 6.68 due October 28 Introduction to inference Estimating with confidence Confidence interval A confidence interval is a range of values with an associated probability or confidence level C . The probability quantifies the chance that the interval contains the true population parameter. Uncertainty and confidence Although the sample mean, , is a unique number for any particular sample, if you pick a different sample you will probably get a different sample mean. In fact, you could get many different values for the sample mean, and virtually none of them would actually equal the true population mean, . x 95% of all sample means will be within roughly 2 standard deviations (2 / n ) of the population parameter . Because distances are symmetrical, this implies that the population parameter must be within roughly 2 standard deviations from the sample average , in 95% of all samples. x : 95% confidence interval for if is known 4.2 is a 95% confidence interval for the population parameter . The equation says that in 95% of the cases, the actual value of will be within 4.2 units of the value of ....
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 Spring '08
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