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Minitab DOE Tutorial interpretation

# Only factors a b c d ab and bc are selected dr

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Only factors A, B, C, D, AB and BC are selected.

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Dr. Jianbiao (John) Pan Minitab Tutorials for Design and Analysis of Experiments Page 20 of 32 Step 6: Validating the assumptions again The results for the re-analysis show that the normality and constant variance assumptions were met. Step 7: Interpreting the ANOVA Results ANOVA table is shown in the session window as below. P-value A small (<0.05, a level of significance) p-value indicates that the four main factors and 2 interactions have statistically significant effect on the response.
Dr. Jianbiao (John) Pan Minitab Tutorials for Design and Analysis of Experiments Page 21 of 32 Step 8. Plots for the main effects and interaction effects The ANOVA table shows that all four factors are significant and there are significant interactions between “Lens placement” and “Laser placement”, and between “Laser placement” and “Laser facet power”. As stated before, if the interaction is significant, ignore the main effect of these factors and only present the interaction plot. Since the factor “Fiber alignment” has no interaction with other factors, the main effect plot of “Fiber alignment” is meaningful. Thus, the interaction plot of “Lens placement” and “Laser placement”, interaction plot of “Laser placement” and “Laser facet power”, and main effect plot of “Fiber alignment” should be displayed. Plots for the main effects and the interaction effects can be obtained by clicking Stat Æ DOE Æ Factorial Æ Factorial Plots . In the dialogue box, check Main Effect Plots and Interaction Plots . - Click Setup button for Main Effect Plot . In the dialogue box appears, select “Optical output power” for Responses and “Fiber alignment” for Selected factor. Then Click OK. Note that multiple main factors’ effect plot can be setup in the dialogue box although in this example only one factor is displayed. - Click Setup button for Interaction Plot . In the dialogue box appears, select “Laser facet power” and “Laser placement” for Selected factors . Then Click OK. - Click OK again to obtain the plots. - Following same procedure, another interaction plot, “Lens placement” vs. “Laser placement” can be obtained.

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Minitab Tutorials for Design and Analysis of Experiments Page 22 of 32 Regression Model From the session window, we can get the estimated coefficients for the regression model as follows: Optical output power = 1.527 + 0.824* (Laser facet power) - 0.0378* (Laser placement) - 0.025* (Lens placement) - 1.498* Fiber alignment - 0.021* (Laser facet power*Laser placement) - 0.034* (Laser placement*Lens placement) Contour Plot and Surface Plot Click Stat Æ DOE Æ Factorial Æ Contour/Surface Plots… In the pop-up window, check both Contour plot and Surface plot . You may click Setup button and change the setup in the pop-up window.
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Only factors A B C D AB and BC are selected Dr Jianbiao...

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