STAT 111 Lecture Notes - Lecture 11: Confidence Interval, Standard Deviation, Sampling Distribution
27 Feb 2019
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Document Summary
To create a confidence interval we need two things: 95% ci = statistic +/- 2 x se. We only need one sample for a statistic, but we need many samples to create a sampling distribution. We create a population to sample from a technique called bootstrapping . In practice, we don"t actually make infinite copies of the sample. But, we can do this by sampling with replacement from the sample we have (each unit can be selected more than once) The standard deviation of the bootstrap distribution is equal to the estimate of the standard error of the best estimate. Option 1: estimate the standard error of the statistic by computing the standard deviation of the bootstrap distribution and then generate a 95% confidence interval. An increased level of confidence = a wider confidence interval. These methods for creating a confidence interval only work if the bootstrap distribution is smooth and symmetric.
