Effect in a DSD having issues with LOD runs

Question

Hi,

I'll have a discussion with a customer soon on the resulting effect in a DSD experiment, when some runs will have an lod issue (limit of detection). I know GenReg can handle this censored situation, however how does it affect the power and predictive performance of the DSD havin 1 or even more runs with lod?

Any experience or rule of thumb would be highly appreciated. I thought about checking the Design power through evaluate design after the runs have been executed. However, evaluate design does not take into account the DSD structure, so I'm not sure if this is misleading anyhow, and even more with LOD in place.

Thanks,

Martin

Phil_Kay · Accepted Answer

Hi Martin,

It will negatively affect power. Fundamentally, there is less information in a <LOD data point.

But I don't think there are any rules of thumb about this. And determining the power will be very difficult. I don't think the power simulation capabilties in JMP Pro could be used in this situation.

Having said all that, analysing in Gen Reg with the <LOD values as censored is going to be better than not using those rows or substituing 0.

Cheers,

Phil

malcolm_moore1 · Accepted Answer

Just to add to what Phil said. Take a pragmatic approach: learn what you can from the data collected and if needed augment your data to learn more (which might be adding replicates to increase confidence or adding runs to explore a wider space or higher order model or something else). Treat learning from data as a continual (iterative) process not a one-shot thing.

Jason_Wiggins · Accepted Answer

Hey Martin,

Here is a discovery talk on the subject

https://community.jmp.com/t5/Discovery-Summit-2014/Using-JMP-to-Analyze-Data-From-a-Designed-Experiment-With-Some/ta-p/21864

This came from my team at US Synthetic. It has video and .pdf report. No data were made available as it was fairly sensitive at the time even anonymized. I can give some additional background if you find it helpful.

J