Where SEM is the standard error of measurement of Ī or ∆ Īprist , n is the number particles in the sample, and SEM i is the i th SEM P or SEM ∆P value in our sample of particles (depending on the parameter being calculated). Sampling uncertainty arises from variability in the dataset due to measuring only a subset of the total population. It is determined by dividing the standard deviation of the sample (σ) by the square root of the sample size (n):