Hi community,
I have conducted a Plackett-Burman DOE for 9 continuous factors measuring 3 different responses (viability, proliferation, gene expression). For one of the responses (gene expression), I actually measure the response three times for each treatment - so these are not independent replicates. I would like to add a random effect in the model that JMP fits for this response. How can I do this practically? Or is this not possible on the JMP platform?
Thank you very much
Sara
Hi @SaraA,
Repetition and Replication are two different techniques that can be combined to reduce costs and variation. Repetition is about making multiple response measurements on the same experimental run (same sample without any resetting between measurements), while replication is about making multiple independent randomized experimental runs (multiple samples with resetting between each runs) for each treatment combination.
- Repetitions only reduce the variation from the measurement system (for example by using the average of the repeated measurements).
- Replications reduce the total experimental variation (process + measurements) in order to provide an estimate for pure error and reduce the prediction error (with more accurate parameters estimates).
I'm not entirely sure how/why you would treat the repetition as a random effect ?
What is your problem or reason behind using several repeated measurements for this response ?
There might be multiple ways to deal with your repetitions :
- If you have high variation from measurement system, you can try using the average of the three runs to reduce the measurement variability.
- You can also use a Mixed Model for repeated measurements : Example of Repeated Measures
- You can also use the repetition (number) as a random effect in your model. It will give you an information about the variance related to the response and its significance, and help identify fixed effects more easily.
If you would like to have more guidance, it would be helpful to have more context and possibly a toy dataset to test.
Hope this answer will help you,
