The confirmatory cut-off for morphine in urine drug testing is 300 ng/mL according to AS/NZS4308. A testing laboratory h

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The confirmatory cut-off for morphine in urine drug testing is
300 ng/mL according to AS/NZS4308.
A testing laboratory has the following Quality Control data.
What should be the working cut-off for morphine based on the
measurement uncertainity of the test method?
Date High QC 350 ng/mL
10/2/2021 320
10/3/2021 330
10/4/2021 370
10/5/2021 390
10/6/2021 345
10/7/2021 365
10/8/2021 350
10/9/2021 320
10/10/2021 330
10/11/2021 380
10/12/2021 325
10/13/2021 375
10/14/2021 383
10/15/2021 374
10/16/2021 376