QTM 100 Lecture Notes - Lecture 4: Central Limit Theorem, Interval Estimation, Randomized Experiment
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The probability that this method produces an interval that contains the true parameter value is called the con dence level. The con dence level is a number close to 1, and is most commonly 0. 95. You can think of this as measuring the error caused by using a sample rather than the whole population. The margin of error is given by the standard error of the statistic multiplied by some t-score or z-score (everything after the ): con dence interval for a population proportion: Calculate the standard error of p: se p =p p(1 p)/n. Identify appropriate z-score (need to know con dence level) Calculate the interval: p zscore se p: con dence interval for a population mean: Calculate the standard error of x: se x = s/ n. Identify appropriate t-score (need to know con dence level and degrees of freedom, df = n 1)