English to Polish Other Environment & Ecology general

Tekst o badaniach mikrobiologicznych wody.

For assessment of counting uncertainty repeatability, the plates or MPN tubes/wells are counted twice by the same analyst familiar with the method. The duplicate counts for each test, denoted by 𝑥1 and 𝑥2, are tabulated and their sums (𝑥1 + 𝑥2) and differences (𝑥1 – 𝑥2) calculated. From these the relative variance (𝑢2rel,L) of each pair is calculated using the formula 𝑢2rel,L=2(𝑥1−𝑥2 / 𝑥1+𝑥2)2. The relative variances for the number of samples (typically 30) are summed and the mean calculated. The repeatability of counting for the method and specific analyst is the square root of this value. Ideally this value should be below < 0.02 but is acceptable up to < 0.1. Values of repeatability of > 0.1 need to be investigated to determine the cause of the high variability.