DoE CCDHello,
I created a series of experiments using DoE (effect surface design). After conducting the experiments, I obtained a Pareto chart at a significance level of 0.02, in which a reference line (blue line) is drawn. I would like to know what value my reference line is? Can I have the value calculated?
Thank you very much
Greetings
Design of ExperimentsRe: DoE CCDHi @ZE : Welcome to the forum. It is the critical value from the t distribution. It depends on alpha (0.05 by default) and the error degrees of freedom (from the ANOVA table). In JMP they are calculated (+/-), respectively, as shown below (where df = Error DF from ANOVA table).
-t Quantile( 0.975, df ), <BR />t Quantile( 0.975, df )
This is explained in the Sorted Estimates help:
Sorted Estimates (jmp.com)
Re: DoE CCDHi MRB3855
Thanks for the quick reply. I had 15 runs and set the alpha value to 0.02. Is there no way in the software to give me the value for the blue line (reference line)? I would like to create a diagram for my report and need the value for this line. In Minitab, I was given a value of 3.36 for the blue reference line.
Many thanks in advance.
Re: DoE CCDHi @ZE Here ya go.
t Quantile( 0.01, 5 ) and t Quantile( 0.99, 5 )
In general, t Quantile (alpha/2, Error df) and t Quantile ( 1-alpha/2, Error df)
Re: DoE CCDHi @MRB3855
I appreciate that. The main problem is that I don't get the same value as with Minitab (critical t-value = 3.36) and that makes me a bit unsure. I have 3 factors that have changed in three levels and occur 5 times each in the trials (15). So I have 14 DF and when I read the t-value at the 0.02 and 14 DF significance levels, I get 2.62.
Re: DoE CCDHi @ZE : You have 15 total runs? If so, you have 9 terms (3 main effects, 3 quadratic effects, and 3 pairwise interactions) in your model and that leaves only 5 df for Error. So 3.36 is correct; you have 14 df Total, but it is the Error df that matters.
Or am I misunderstanding?
Re: DoE CCDHi @MRB3855
no, you're right. i'm sorry, i made a small logical mistake and always calculated with the total degree of freedom.
