1820 G Mohanty et al. /Materials Research Bulletin 43(2008)1814-1828 20.00 15.0 10003 D: Deposition Time Fig. 2. A typical interaction effect between concentration and deposition time on deposition. interesting to note that all interaction factors containing B(electrode separation)except BC contribute negatively towards the weight of alumina deposit obtained. This is expected as increase in electrode separation results in decrease in electric field which results in lesser rate of deposition. Also electrode separation term is inversely proportional to the quantity of particles deposited electrophoretically according to Hamaker equation [26, 29] 2Z ANOVA Analysis of variance(ANOVA)of the selected model was carried out. ANOVA is a statistical technique which sub- divides the total variation of a set of data into component parts associated with specific sources of variation for the purpose of testing a hypothesis on the parameters of a model. Tables 4a, 4b and 5 show the results of analysis of variance for the weight of alumina deposited Sufficient degrees of freedom were available for the evaluation of the model as can be seen in Table 6. Large degrees of freedom increase the discrimination between adequate and inadequate models. The conclusions of the analysis of variance apply to the transformed data. High model F-value of 688.66 indicated that the model is significant(Tables 4a and 4b). Insignificant curvature F value of 2. 29 validated our initial assumption of approximate linearity of the response variable in the design space Hence design augmentation by introduction of higher order terms to the model was felt unnecessary. Lack of fit is the variation of data around the fitted model. An F-value of 1.99 corresponding to insignificant lack of fit suggested that the model fits well with the data. Hence the model was used to navigate the design space Table 5 Additional data from anova 0.00437 q precision 97.388interesting to note that all interaction factors containing B (electrode separation) except BC contribute negatively towards the weight of alumina deposit obtained. This is expected as increase in electrode separation results in decrease in electric field which results in lesser rate of deposition. Also electrode separation term is inversely proportional to the quantity of particles deposited electrophoretically according to Hamaker equation [26,29]. 2.7. ANOVA Analysis of variance (ANOVA) of the selected model was carried out. ANOVA is a statistical technique which sub￾divides the total variation of a set of data into component parts associated with specific sources of variation for the purpose of testing a hypothesis on the parameters of a model. Tables 4a, 4b and 5 show the results of analysis of variance for the weight of alumina deposited. Sufficient degrees of freedom were available for the evaluation of the model as can be seen in Table 6. Larger degrees of freedom increase the discrimination between adequate and inadequate models. The conclusions of the analysis of variance apply to the transformed data. High model F-value of 688.66 indicated that the model is significant (Tables 4a and 4b). Insignificant curvature F￾value of 2.29 validated our initial assumption of approximate linearity of the response variable in the design space. Hence design augmentation by introduction of higher order terms to the model was felt unnecessary. Lack of fit is the variation of data around the fitted model. An F-value of 1.99 corresponding to insignificant lack of fit suggested that the model fits well with the data. Hence the model was used to navigate the design space. 1820 G. Mohanty et al. / Materials Research Bulletin 43 (2008) 1814–1828 Fig. 2. A typical interaction effect between concentration and deposition time on deposition. Table 5 Additional data from ANOVA S.D. 0.00437 Mean 0.19 C.V. (%) 2.24 PRESS 0.00127 R2 0.9988 Adj R2 0.9974 Pred R2 0.9904 Adeq precision 97.388