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F and P-value in L9 Taguchi Design


Forum Moderator
Staff member
17 df is correct. When you replicated (not repeated) the experiment, that provided the additional degrees of freedom. Instead of 9 runs, you had 18 runs, which provided 17 df.

A repeat is multiple samples taken from the same experimental run.
A replicate is the same experimental conditions run multiple times with other experimental conditions intervening.
Thank you very much.

In fact when I realized this problem, I quickly repeated each of the runs. The ANOVA results showed a good outcome. However, because I have already stated in my experiments that I used L9, the new GLM results showed 17 total degree of freedom instead of 8 which I am quite skeptical to report in my research results.
FYI: I have seen the link for the book.

What do you suggest in this case? Should I just go ahead to report it as it is shown in the ANOVA table?

This is the out of the ANOVA after repeating each of the runs

Var DoF) SS MS F-value P-value (%)

A 2 1335.90 667.95 1471.30 0.00 63.40
B 2 305.74 152.87 336.73 0.00 14.51
C 2 448.89 224.44 494.38 0.00 21.30
D 2 12.40 6.20 13.65 0.01 0.59
Error 9 4.09 0.45 0.19
Total 17 2107.01
Hi, I came through this post, because I have the same problem analyzing my L9 Taguchi with 4 parameters. Actually I already did 3 replications but still don't know how to tell Minitab that there are replications. How did you manage to do the ANOVA that you had 17 total degrees of freedom instead of 8?

I would be glad if you could help me out with this.


Forum Moderator
Staff member
Dr. Taguchi never intended for his designs to be replicated and Minitab followed his methodology precisely. The only way around this issue is to use GLM (General Linear Model) to analyze the results. GLM will recognize the replications as long as you keep them in a single column.
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