Quantifying Uncertainty in Ecosystem Studies

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3/02/2015 2:20 pm  #1


How do you deal with analytical data that's below detection limit?

I know many labs use half of the detection limit. Is this what everyone does? Please reply with  the standard practice of your lab!

Last edited by Craig See (3/02/2015 4:30 pm)

 

3/04/2015 1:10 pm  #2


Re: How do you deal with analytical data that's below detection limit?

This paper has a method to redistribute it in the case of a lognormal distribution. I can't tell if it is generalizable to any other distributions though.

Kroll, C. N. and J. R. Stedinger (1999): Development of regional regression relationships with censored data.  Water Resources Res. 35, 3, 775-784. DOI:10.1029/98wr02743

 

3/23/2015 1:03 pm  #3


Re: How do you deal with analytical data that's below detection limit?

That makes the distribution more realistic.  At Hubbard Brook, I think they use half of the detection limit, which is evident in the data set (for example, NH4 in streams).  Which could be good or bad.  You wouldn't want someone to try to analyze the variation below detection.

 

4/29/2015 12:28 pm  #4


Re: How do you deal with analytical data that's below detection limit?

I know it is standard procedure in our lab and in industry is to use half the detection limit.  Any values below this are not reliable data; you can reasonably state that those values are low, but wouldn't be able to state how low they are.  This highlights the importance of QA/QC to continually monitor the detection limits on instrumentation.

 

10/11/2016 9:36 pm  #5


Re: How do you deal with analytical data that's below detection limit?

Great. where do I find the data file and how do I let Accountz know where it is after I have moved it?

 

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