Can I add a factor to an existting DOE and/or change the values of any run in an existting DOE?

[#1]

Hi, I developed a DOE model with 3 factors (one categorical) for a specific time (7 days) containing 16 runs. Later I used the same DOE but now for samples (runs) with a loger time (28 days). Now, I have decided to add the time as a factor but I want to keep the runs that a I have (16 runs for 7 days, and 16 runs for 28 days); to improve the quality of the model I decided to add center points to the design (time 17.5 days): I added 4 runs, one for each value of the categorical factor. How can I do that, keeping some previous runs? In the augmented design it is not allowed to add a new factor, or is it allowed (if yes, I do not know how to do it). So, I decided to develop a new DOE, now with 4 factors (including time as a factor) and with 30 runs (16 for 7 daus, 4 for 17.5 days, 16 for 28 days), but the table generated by jmp has some runs different from the previous 16 runs (for 7 and 28 days); can I change the values of any factor in this new DOE in order to keep the previous runs, is this alllowed wtihout compromising the accuracy? Or simply I cannot perform this analysis?

[#2]

Some advice for getting better feedback is to include your data table.

The situation is not described well enough to be confident in my response, however, if I understand correctly, there is a factor called cure time  that you wanted to test at 2 levels.  Unfortunately, you did not anticipate that cure time does not work at the low level you set, so those treatments can't be run.  It seems to me that you should be able to analyze other factors in  your experiment, you just will have no way to include cure time or cure time by factor interactions i your analysis.

Statistical significance is a conditional statement!  Sources of variation (design factors) are compared to other sources of variation (noise inside the DOE changing treatment-to-treatment) under a certain set of conditions, the noise held constant during the DOE (aka inference space).  If any of those sources change, so may statistical significance.