Repeat the previous exercise, only now compare the marginal 20% trimmed means using the R function yuend with the argument tr=0.2. Verify that the p-value is 0.2209.

Exercise
Carnegie Mellon University maintains a site with many interesting data sets for use in the classroom. Some of these data sets are stored at http://stat.cmu.edu/DASL/allsubjects.html.

Go to this web page, look under psychology, download the file called scents and read the file into an R variable called scent. The last six columns contain the time participants required to complete a pencil and paper maze when they were smelling a floral scent and when they were not. The columns headed by U.Trial.1, U.Trial.2, and U.Trial.3 are the times for no scent, which were taken taken on three different occasions.

Compare scent and no scent data for occasion 1 using difference scores via the command trimci(scent[,7]-scent[,10],tr=0), so the mean of the difference scores is being used. Verify that the p-value is 0.597.