<p>This International Standard gives guidelines for the evaluation of uncertainty in quantitative microbiological</p>
<p>analyses based on enumeration of microbial particles by culture. It covers all variants of colony count methods</p>
<p>and most probable number estimates.</p>
<p>Two approaches, the component (also known as bottom‑up or step‑by‑step) and a modified global (top‑down)</p>
<p>approach are included.</p>
<p>The aim is to specify how values of intralaboratory operational variability and combined uncertainty for final</p>
<p>test results can be obtained.</p>
<p>The procedures are not applicable to methods other than enumeration methods.</p>
<p>NOTE 1 Most annexes are normative. However, only the annexes relevant to each case are to be applied. If the choice</p>
<p>is the global approach, then all normative annexes that belong to the component approach can be skipped and vice versa.</p>
<p>NOTE 2 Pre-analytical sampling variance at the source is outside the scope of this International Standard, but needs</p>
<p>to be addressed in sampling designs and monitoring programmes.</p>
<p>NOTE 3 The doubt or uncertainty of decisions based on the use of analytical results whose uncertainty has been</p>
<p>estimated is outside the scope of this International Standard.</p>
<p>NOTE 4 The extra‑analytical variations observed in proficiency tests and intercalibration schemes are also not</p>
<p>detailed in this International Standard, but it is necessary to take them into consideration in analytical control. The use</p>
<p>of intercalibration data in uncertainty estimation offers the possibility for the bias between laboratories to be included</p>
<p>(Nordtest Report TR 537[12]).</p>
Registration number (WIID)
45348
Scope
<p>This International Standard gives guidelines for the evaluation of uncertainty in quantitative microbiological</p>
<p>analyses based on enumeration of microbial particles by culture. It covers all variants of colony count methods</p>
<p>and most probable number estimates.</p>
<p>Two approaches, the component (also known as bottom‑up or step‑by‑step) and a modified global (top‑down)</p>
<p>approach are included.</p>
<p>The aim is to specify how values of intralaboratory operational variability and combined uncertainty for final</p>
<p>test results can be obtained.</p>
<p>The procedures are not applicable to methods other than enumeration methods.</p>
<p>NOTE 1 Most annexes are normative. However, only the annexes relevant to each case are to be applied. If the choice</p>
<p>is the global approach, then all normative annexes that belong to the component approach can be skipped and vice versa.</p>
<p>NOTE 2 Pre-analytical sampling variance at the source is outside the scope of this International Standard, but needs</p>
<p>to be addressed in sampling designs and monitoring programmes.</p>
<p>NOTE 3 The doubt or uncertainty of decisions based on the use of analytical results whose uncertainty has been</p>
<p>estimated is outside the scope of this International Standard.</p>
<p>NOTE 4 The extra‑analytical variations observed in proficiency tests and intercalibration schemes are also not</p>
<p>detailed in this International Standard, but it is necessary to take them into consideration in analytical control. The use</p>
<p>of intercalibration data in uncertainty estimation offers the possibility for the bias between laboratories to be included</p>
<p>(Nordtest Report TR 537[12]).</p>
