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Published byAlberta Stafford Modified over 9 years ago
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Introduction to design Olav M. Kvalheim
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Content Making your data work twice Effect of correlation on data interpretation Effect of interaction on data interpretation
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Chemometrics/Infometrics Design of information-rich experiments and use of multivariate methods for extraction of maximum relevant information from data
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Making your data work twice
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What is Information? A B C A - mean value, no standard deviation given B - mean value with standard deviation given, large value of stand. dev. C - mean value, low standard deviation
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A B Hotelling (1944) Ann. Math. Statistics 15, 297-306 Measurement strategy? Unknowns Calibration Weights
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The univariate weighing design Weigh A and B separately m A ± A m B ± B A = B = Precision is for both A and B
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The multivariate design Weigh A and B jointly to determine sum and difference: m A + m B =S m A - m B =D m A = ½S + ½D m B = ½S - ½D Precision is 0.7 for both A and B Precision for S Precision for D
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Precision is improved by 30% by using a multivariate design with the same number of measurementsas for the univariate! Univariate vs Bivariate strategy
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With N masses to weigh, a multivariate design provides an estimate of each mass with a precision The larger the number of unknowns, the larger the gain in precision using a multivariate weighing design. Univariate vs Multivariate weighing
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Effect of correlation on data interpretation X1 X2X1 X2
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Example Process output is function of temperature and amount of catalyst
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Correlation between amount of catalyst and amount produced Strong positive correspondence
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Correlation between Temperature and Produced amount Weak positive correspondence
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Conclusion from correlation analysis Increase amount of catalyst and temperature to increase production
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Result of test Produced amount was lowered!
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Bivariate Regression Model Produced amount = 300 + 2.0 * Catalyst - 0.5 * Temperature
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Correlation between temperature and amount of catalyst Strong positive correspondence
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Solution to correlation problem Multivariate Design - Change many process variables simultaneously according to experimental designs
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Effect of interaction on data interpretation X1X2X1X2
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The yield of a chemical reaction is a function of temperature (t) and concentration (c). y = f (t,c) The task Optimise the yield for the reaction!
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Concentration, M Temperature, ºC 0.10.2 140 160 150 170 75 6070 50 4045 Response surface in the presence of interaction
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Univariate design (COST) Multivariate design Information Number of experiments Efficiency of information extraction
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Multivariate Design vs. Univariate Design Correct Models Possible (Interactions) Efficient Experimentation Improved Precision/Information quality
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