Methods in enzymology
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If one has a convoluted fluorescence decay and wishes to analyze it for a sum of exponential, then one can begin by asking either of two questions: (1) What sum of exponentials best fits the data? (2) What physical decay parameters gave rise to the data? At first these two questions may sound equivalent; in fact, they represent different philosophical approaches to data analysis. In resolving the first question, one adjusts the decay parameters until a calculated curve agrees within arbitrarily chosen limits to the original data. This is what we did in the fourth section of Table II. ⋯ Perhaps question (1) could be modified to include all of the errors that might be present in the data; but then, how would one decide which errors to include and whether an error is present? What fitting criterion would tell one this? Why choose a method which depends so strongly on this information when robust alternatives exist? As a rule, fitting should not be used as a criterion for correct decay parameters, unless all of the significant nonrandom errors have been included in the fit. If one fits the data but has not incorporated an important error, then the best fit will necessarily give the wrong answer. The method of moments provides clear criteria for accepting or rejecting an analysis.(ABSTRACT TRUNCATED AT 400 WORDS)