Data case studies
Simon Vaughan · 2013
This appendix discusses some of the datasets that are used as examples throughout the text. They are all available online from www.cambridge.org/9781107607590. Although R can load files directly from the web, it is good practice to download the individual files to a local directory so that they can be used off-line. The files needed for this chapter are rutherford.dat, reynolds.txt, hipparcos.txt.gz and pedroni.dat. Michelson's speed of light data A. A. Michelson – known to students of physics for the famous Michelson-Morley experiment – made great advances in precision optical measurements, particularly the measurement of the speed of light. Here we shall use a set of 100 measurements of the speed of light in air taken in summer 1879 originally published by Michelson (1882) and reproduced by Stigler (1977). The first few data values are shown in Table B.1. Each of the numbers represents the speed recorded in one ‘run’ of the apparatus, in units of km s −1 . Each run was in fact an average of several individual measurements. The 100 numbers, which together form a sample , are divided into five groups of 20, each group labelled an ‘experiment’. The speed measurements are in principle continuous, but Michelson's data have been rounded to the nearest 10 km s −1 . Stigler (1977) applied Michelson's own corrections to the modern value of c to give a value of 299 734.5 km s −1 for the speed of light in air.