Bias in estimated mean

"Bias" is defined here as a systematic over- or underestimation of the true site mean. Bias is generally introduced when the sampling strategy or sample collection method yields observations that are not truly independent or representative of site conditions. For example, use of a systematic sampling pattern that coincides with spatial trends in the data may produce a data set that disproportionately represents a range of concentrations; poor sample collection techniques may underrepresent actual soil characteristics.Accuracy reflects a combination of precision (reproducibility) and bias (systematic over/underestimation). The RSD of replicate ISM means is a measure of precision.