Hi Colleagues
While doing RSM in design expert I am getting thses two options for generating the final equation
1. Final Equation in Terms of Coded Factors. 2. Final Equation in Terms of Actual Factors. There is a huge difference in the coefficient values between the equations. Not getting idea of what does they actually mean and why this difference is!
Also any idea of which will be my final equation for representing the study. Many thanks.
Hello all
there is something important to be noted.
Design expert uses the coded-based equation to plot all the graphs and optimize your data. If you cahnge the actual values of your input variables without changing your responses and re-analyse your data, you will see that the equation in terms of coded values remains the same but the other equation which is in terms of the actual values will be changed.
If you also take a look at the hints available in the ANOVA section, you will findout that it has been stated the equation in terms of actual values is used to predict the response based on the actual values if your independent variables and this equation should NOT be used to determine the relative impact of each factor.
good luck
The coded equations enable the comparison between the factors in terms of directions and magnitudes of effects by simply comparing the coefficients. So, the coded equation might be better to present in your study. on the other hand, the equations in actual terms are not helpful in that comparison while they can be used for the prediction of the responses. So, you can use either the coded or actual equations for predicting a response but you have to substitute for the factors and other regression terms in coded values for the coded equations or in actual values in actual values equations. If you are using the optimization function in "design expert" you do not have to care about which equation to use as the software will calculate it automatically
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