G Mohanty et al./ Materials Research Bulletin 43(2008)1814-1828 list and their contribution towards response 56.1126 B (Electrode separation 4.65128 AB 0.00129 Mode ACD ABCD 00274 Mode 0.03325 Lack of fit Pure em Model"indicates the inclusion of the factor in the final regression model while" error"indicates exclusion of the effects as they were found to be Table 4b Analysis of variance(ANOVA)of the selected model Source Sum of squares Degrees of freedom Mean square F-value p-Value Prob>F Model 0013159 <0.0001 Significa -concentration 0.073951 0.073951 <0.0001 B-elec Sep 0.00613 0111 000613 320.7922 <0.0001 C-app potential 0.011282 011282 <0.0001 D-dep time 00331 0.033175 <0.0001 0.000689 0.000689 0.000645 0.000645 33.72949 0.00432 <0.0001 0.00019 003 0.000774 000774 0.000438 0.000438 Curvature 0.0000438 0.1684 Residual 0.000153 0.0000191 0.000118 0000235 1994685 Not signif Pure error 0.0000354 853 00000118 electrode separation. The dominant interaction effect is AD(interaction between concentration and deposition time) and is shown in Fig. 2. This is expected as both concentration and deposition time are the two major contributing actors 2.6. Model refinemen Model refinement is primarily achieved through exclusion of the factors that are found to be insignificant. Exclusion of insignificant variables releases degrees of freedom for the calculation of confidence intervals[28]. Factor effects with a significance level of 0.05 or lower(p-value <0.05; 95% confidence level)were included in the Te Acd and aBCD sion model. This resulted in inclusion of 10 effects in the model. The positive effects were: A, C, D, AD, AC, BC, CD, while the negative effects were: B, AB, BD, ABC, ABD and BCD. An effect is said to be positive when increase in its level results in increase in the response and negative when increase in its level results in decrease in the response. It iselectrode separation. The dominant interaction effect is AD (interaction between concentration and deposition time) and is shown in Fig. 2. This is expected as both concentration and deposition time are the two major contributing factors. 2.6. Model refinement Model refinement is primarily achieved through exclusion of the factors that are found to be insignificant. Exclusion of insignificant variables releases degrees of freedom for the calculation of confidence intervals [28]. Factor effects with a significance level of 0.05 or lower ( p-value  0.05; 95% confidence level) were included in the regression model. This resulted in inclusion of 10 effects in the model. The positive effects were: A, C, D, AD, AC, BC, CD, ACD and ABCD while the negative effects were: B, AB, BD, ABC, ABD and BCD. An effect is said to be positive when increase in its level results in increase in the response and negative when increase in its level results in decrease in the response. It is G. Mohanty et al. / Materials Research Bulletin 43 (2008) 1814–1828 1819 Table 4a Effects list and their contribution towards response Effects list Term Contribution (%) Model A (Concentration) 56.1126 Model B (Electrode separation) 4.65128 Model C (Applied potential) 8.56088 Model D (Deposition time) 25.1722 Model AB 0.52309 Model AC 0.48906 Model AD 3.27755 Error BC 0.00129 Model BD 0.14437 Model CD 0.58734 Error ABC 0.00806 Model ABD 0.33236 Error ACD 0.00163 Error BCD 0.07546 Error ABCD 0.00274 Model Curvature 0.03325 Error Lack of fit 0 Error Pure error 0.02682 ‘‘Model’’ indicates the inclusion of the factor in the final regression model while ‘‘error’’ indicates exclusion of the effects as they were found to be insignificant. Table 4b Analysis of variance (ANOVA) of the selected model Source Sum of squares Degrees of freedom Mean square F-value p-Value Prob > F Model 0.131594 10 0.013159 688.6568 <0.0001 Significant A-concentration 0.073951 1 0.073951 3870.007 <0.0001 B-elec Sep 0.00613 1 0.00613 320.7922 <0.0001 C-app potential 0.011282 1 0.011282 590.4317 <0.0001 D-dep time 0.033175 1 0.033175 1736.095 <0.0001 AB 0.000689 1 0.000689 36.07678 0.0003 AC 0.000645 1 0.000645 33.72949 0.0004 AD 0.00432 1 0.00432 226.0479 <0.0001 BD 0.00019 1 0.00019 9.95687 0.0135 CD 0.000774 1 0.000774 40.50827 0.0002 ABD 0.000438 1 0.000438 22.92264 0.0014 Curvature 0.0000438 1 0.0000438 2.293185 0.1684 Not significant Residual 0.000153 8 0.0000191 Lack of fit 0.000118 5 0.0000235 1.994685 0.3023 Not significant Pure error 0.0000354 3 0.0000118