Stats Final Notes 2 - (Chapter 19 Confidence Intervals 95 of the time the mean will fall between these values 4 step process of calculating confidence

Stats Final Notes 2 - (Chapter 19 Confidence Intervals 95...

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(Chapter 19) Confidence Intervals 95% of the time, the mean will fall between these values. 4 step process of calculating confidence intervals: 1. State – what parameter do you want to estimate and at what confidence level? 2. Plan – hypotheses; determine statistical method. 3. Do – Calculate z-statistic to find P-value 4. Conclude – interpret interval ie. The mean will fall within these values _ % of the time. Calculate confidence interval using ´ x± z ¿ σ √ n Margin of error of a confidence interval changes w sample size and level of confidence (C). Given confidence level and other information, find the sample size required to obtain a confidence interval of specified margin of error. Sources of error not included in margin error eg. undercoverage/ non-response Chapter 20: Inference about a Population Mean Standard error of the sample mean is Sx √n where Sx is the sample standard deviation. t distribution – different shape than the standard Normal curve. Depends on degrees of freedom. T distribution vs. standard normal distribution – similar in curve shape; spread of t is greater; t have

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