Statistical Sciences 1024A/B Chapter Notes - Chapter 21: Confidence Interval

• School: Western University
• Department: Statistical Sciences
• Course: Statistical Sciences 1024A/B
• Professor: Lori Murray

Document Summary

Comparing two populations or two treatments is one of the most common situations encountered in statistical practice. We have two independent simple random samples (srs) from two distinct populations. Both populations are normally distributed with unknown means and standard deviations. In practice, it is enough that the distributions have similar shapes and that the data have no strong outliers. 1 is the mean of the first population. 2 is the mean of the second population. We want to make inferences about 1 and 2 or 1 - 2. Note that the degrees of freedom may not be a whole number. Option 2: without software, use the smaller of (n1 1). The two-sample confidence interval for 1 - 2 is: The choice of the minimum of (n1 1) and (n2 1) as degrees of freedom to determine t* will result in a wider confidence interval than the exact/correct degrees of freedom (option 1)