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(Chapter 19) Confidence Intervals95% 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-value4.Conclude – interpret interval ie. The mean will fall within these values _ % of the time.Calculate confidence interval using ´x± z¿σ√ nMargin 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-responseChapter 20: Inference about a Population MeanStandard error of the sample mean is Sx√nwhere 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