Confidence intervals 2

Download: CalculatingParametricCI-mean_init.xlsx

Download: Screencast-Slides.pdf

Introduction

This screencast demonstrates how to calculate parametric confidence intervals for the mean and trimmed mean in Excel, both manually and using the CLS-Stats lambda functions. I would say that you should be able to calculate the untrimmed mean parametric CI without using the tmean function, if necessary. Calculating the parametric CI of the trimmed mean is a little more tedious but it is nice to see it done once so that you understand how it was calculated.

Learning Outcomes

• Understand what a parametric confidence interval is
• Learn how to calculate the parametric confidence interval of the (untrimmed) mean manually, without using tmean
• Learn how to use and interpret tmean to generate confidence intervals (and conditional confidence intervals using FILTER)
• Learn how to report confidence intervals with the appropriate number of significant figures
• Learn how many values are trimmed in a trimmed mean

Tasks

• Use tmean to calculate the 95% CI for the untrimmed mean
• Report the CIs calculated above
• Manually calculate the parametric CI for the untrimmed mean
• Use FILTER to calculate the 95% CI for the untrimmed mean with two semesters removed from the data
• Use FILTER to calculate the 95% CI for the 25% trimmed mean by gender
• Manually calculate the 95% CI of the 25% trimmed mean and compare to the output of tmean

When you are finished your spreadsheet should look something like the one below.