
130 Data Analysis and Statistics for Geography, Environmental Science, and Engineering
4.8.17 nonparaMetric: Wilcoxon test
Consider the data from a very famous physics experiment by Albert Michelson to measure the speed
of light with an interferometer. The dataset michelson is part of package MASS. The Speed
values are departures from a previously reported speed of light of 299,990 km/s. There are a certain
number of measurements (Run) for each experiment number (Expt)
> data(package=”MASS”)
> data(michelson)
> michelson
Speed Run Expt
1 850 1 1
2 740 2 1
3 900 3 1
Let us explore part of the dataset; say Expt 1 runs 1–20.
> mich <- michelson$Speed[1:20] ...