%0 Journal Article
%T Two-Stage Genetic Algorithm in the Analysis of Biochemical Relations
%A Bar£¿£¿ A£¿IKG£¿L
%A Ayd£¿n ERAR
%J Turkiye Klinikleri Journal of Biostatistics
%D 2012
%I Turkiye Klinikleri
%X Objective: Nonlinear regression analysis is usually used in medical or biochemical areas in order to estimate unknown parameters. Ordinary least squares method can be considered for parameter estimation. However, efficient parameter estimates can not be obtained with the help of this method when errors are autocorrelated. In this paper, a method called two-stage genetic algorithm (TSGA) is proposed in order to obtain efficient parameter estimates. Material and Methods: Two-stage least squares (TSLS) method is preferred in order to overcome the autocorrelation problem. However, the method has some problems in the parameter estimation process if initial values of parameters are not known. Therefore, TSGA can be used in the presence of unknown initial values for nonlinear parameters. In this paper, two data sets taken from Faculty of Pharmacy have been examined on a preferred nonlinear model and it has been noticed that residuals are autocorrelated. Because of both unknown initial values of parameters and the autocorrelation problem among errors, TSGA method has been applied by using MATLAB 7.1. Results: The results obtained by using genetic algorithm (GA) and TSGA have been compared in view of the correlograms. p-values in the correlograms obtained from GA are <0.001 for all lags. This means that the autocorrelation problem exists among errors. However, p-values in the correlograms obtained from TSGA are greater than ?=0.05 for all lags. This means that the autocorrelation problem is removed. Moreover, mean squared error values for TSGA (4.86 and 0.03) are smaller than mean squared error values for GA (11.28 and 0.04). Conclusion: It can be concluded that TSGA can give efficient parameter estimates in the presence of autocorrelated errors.
%K Nonlinear dynamics
%K regression analysis
%K least-squares analysis
%U http://www.turkiyeklinikleri.com/pdf/?pdf=fa2c4e21abbfe71171df0f5ba25e9e99