How does the TOC QBD1200 analyzer option "Reject Outliers" work?

Document ID

Document ID TE8314

Published Date

Published Date 04/07/2022
Question
How does the TOC QBD1200 analyzer option "Reject Outliers" work?
Summary
QBD1200 "Reject Outliers" option
Answer

The "Reject Outliers" option allows the user to have replicates automatically rejected (i.e. not included in reporting and statistics) based on a target Std Dev/RSD. Pretend the user has chosen to do 4 replicates for a drinking water sample and "reject outliers" with a target deviation of 3.0. In that situation, the analyzer will measure all 4 reps and check the RSD to see if the 3.0 % criteria is met. If it isn't, the analyzer software then determines which group of three replicates results in the best RSD and rejects the fourth. If the user chose 5 reps, the analyzer would do the same thing but only reject enough replicates to meet the target RSD %. The analyzer will never discard below 3 reps, though. That's why the option is disabled if the user selects 3 or fewer reps. Below are some examples of what this looks like if the user selects a 3.0% target.

One other thing to note is that the target becomes standard deviation in ppb if the sample average is below 100 ppb. That fits with our reported reproducibility stat of 3.0 ppb std dev or 3.0% RSD and the reasoning behind that change below 100 ppb is the same.


 

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