On Sat, 15 Nov 2003, Jean lobry wrote: > Dear All, > > I'am looking for examples showing that correlation does not imply > causality, the targeted audience consists of undergraduate students > (their first year at the university but in the BioMathStat track). > All practicals are under R. >
There's a nice example we use (data at http://courses.washington.edu/b517/datasets/fev.txt documentation at http://courses.washington.edu/b517/datasets/fevdoc.txt ) These are lung function (FEV1) data on children, taken at routine checkups, and we tell people to do a t.test comparing smokers and non-smokers. There is a large and statistically significant difference -- the smokers have *higher* FEV1, because they are older. In a statistics course for graduate students in public health there are always a few people who see the difference and forget to check the direction... -thomas ______________________________________________ [EMAIL PROTECTED] mailing list https://www.stat.math.ethz.ch/mailman/listinfo/r-help
