Chapter 3
Collecting Data
GIGO: Garbage in; Garbage out.
“Fancy statistical methods will not rescue garbage data.”
Course notes of Raymond J. Carroll [2001].
THE VAST MAJORITY OF ERRORS IN STATISTICS (and, not incidentally, in most human endeavors) arise from a reluctance (or even an inability) to plan. Some demon (or demonic manager) seems to be urging us to cross the street before we have had the opportunity to look both ways. Even on those rare occasions when we do design an experiment, we seem more obsessed with the mechanics than with the underlying concepts.
In this chapter, we review the fundamental concepts of experimental design, the choice of primary and secondary variables, the selection of measurement devices, the determination of sample size, the assumptions that underlie most statistical procedures along with the precautions necessary to ensure they are satisfied and that the data you collect will be representative of the population as a whole. We do not intend to replace a text on experiment or survey design, but to supplement one, providing examples and solutions that are often neglected in courses on the subject.
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