Time course experiments, experimental design

Thus, when statisticians got into the act, there saw a need to retain the information that was not included in the one-at-a-time plans, while still keeping the total number of experiments manageable the birth of statistical experimental designs . Several types of statistical experimental designs have been developed over the years, with, of course,... 

Known Variables — Controllable In any experimental situation, cettain conditions are held constant during the course of the experiment. A batch of copolymer may be made with a measured quantity of catalyst, at a given reaction temperature, and reacted for a certain definite time. The vessel is free of water, die monomers are charged in a definite proportion, and any other conditions that may affect the result are held fixed. The next portion of the experiment may involve one of these conditions controlled at a new level while the others remain fixed. Proper design of experimental programmes presupposes ability to control the important factors so that the variation due to these factors can be calculated. In Chapter VI, experimental designs for various situations are coveted. 

We continue our study of chemical kinetics with a presentation of reaction mechanisms. As time permits, we complete this section of the course with a presentation of one or more of the topics Lindemann theory, free radical chain mechanism, enzyme kinetics, or surface chemistry. The study of chemical kinetics is unlike both thermodynamics and quantum mechanics in that the overarching goal is not to produce a formal mathematical structure. Instead, techniques are developed to help design, analyze, and interpret experiments and then to connect experimental results to the proposed mechanism. We devote the balance of the semester to a traditional treatment of classical thermodynamics. In Appendix 2 the reader will find a general outline of the course in place of further detailed descriptions. 

Pursuit of strategies. The brief outlines above may serve to characterize the possible options in process development. They describe clear-cut, "pure" strategies, but, of course, modifications are possible. For efficient development it is important to decide as early as possible on the merits of the case which tack to take. If the chosen approach is evolutionary or empirical, expected best operating conditions for the eventual plant should dominate the design of the experimental program. In contrast, if the fundamental approach is taken, the clear aim should be to establish networks and mechanisms beyond reasonable doubt with the fewest possible experiments, even if their conditions are far remote from those likely to be employed in the plant. Only when networks and mechanisms are believed to be in hand, should predictions for expected plant conditions be made and verified. An attempt to look at plant conditions while pursuing the fundamental approach is apt to syphon off valuable manpower and time from the principal effort ... 

As the detailed experimental procedure is not subjected to variations by the above strategy, it is advised that the chemist should use his/her experience and chemical intuition to determine the concentrations of the reagent(s) to be added, rates of addition, hold times etc. This is an exception to what has been claimed throughout this book. It is, of course, possible to lay out fractional factorial designs to accomodate also such variations but this would lead to an unnecessary proliferation of the number of experimental runs. If it is suspected that also the detailed experimental procedure may interact with the order of introduction, the experimental procedure as a whole, of course, must be analyzed. If this is not the case, the detailed analysis of the experimental conditions can wait until a suitable introduction order has been found. 

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