Learn by Doing – Confidence Intervals: Means #1
A study was done on pregnant women who smoke during their pregnancies. In particular, the researchers wanted to study the effect that smoking has on pregnancy length. A sample of 114 pregnant women who were smokers participated in the study and were followed until the birth of their child. At the end of the study, the collected data were analyzed and it was found that the average pregnancy length of the 114 women was 260 days. From a large body of research, it is known that length of human pregnancy has a standard deviation of 16 days.
http://phhp-faculty-cantrell.sites.medinfo.ufl.edu/files/2012/12/LBD_11001_164.swf
http://phhp-faculty-cantrell.sites.medinfo.ufl.edu/files/2012/12/LBD_11002_164.swf
This document is linked from Population Means (Part 1).