Isoresponse contour plots

Analysis of variance of the regression did not indicate any significant lack of fit, Lack.of-fit 4 -74 pCnt g gj (a = 5 %). The residual plots in Fig. 12.10 do not show abnormal behaviour. It was therefore assumed that the variation in yield was adequately described by the model. The isoresponse contour projections are shown in Fig.12.11... 

The surface representing the model is called the response surface. Graphically, the response surface can be visualized by drawing 2D contour plots or 3D response surface plots (7). A 2D contour plot shows the isoresponse lines as a function of the levels of two variables, while a 3D response surface plot represents the response, on a third dimension, as a function of the levels of two variables. An example of a 2D contour plot and a 3D response surface plot is shown in Figure 2.18. When more than two factors... 

In a second step, a simplex centroid design was realized with seven design points and six check points. Two responses were optimized consistency and whiteness. Using the second-order equations from this matrix, it is possible to obtain isoresponse graphs. The contour plots are given in Figs. S and 6. The optimal gel must correspond to a gel similar to petrolatum. This optimal zone is reported in Fig. 7 where contour plots of the two responses are superimposed. 

The response surface representing the model can be visualised graphically by means of 2D contour plots and/or 3D response surface plots. In a 2D contour plot, the isoresponse lines are represented as a function of levels of two factors, while in a 3D plot the response is represented on a third dimension, as a function of the factor levels (see Figure 3.24). When more than two factors are examined and modelled, all but two factors need to be fixed at a given level to draw both plots. The optimal or acceptable experimental conditions can be derived from the graphical representation of the model or by mathematical analysis of its equation. 

Instead of using a response surface graph, one often uses a contour plot. This translates the response surface in the same way as a geographical map of a mountainous area. The isoresponse lines can be viewed as the contour lines on the map. 

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