Sample Size and DQO
statisticsMinimum sample size for a target confidence and power, with a power curve.
Decision and Design Parameters
Set your design parameters and run the analysis
The recommended sample size and a power curve will appear here.
What this calculates
Data Quality Objective (DQO) sample-size planning: the minimum number of samples needed to detect a minimum difference (or, for the compliance decision, a proportion difference) at a target confidence and statistical power, for a site-mean-vs-standard test, a two-sample comparison, or a compliance/proportion-exceeding decision - with a power curve showing how achieved power grows with sample size. Also included are the CRV (combined risk value) method for confirming the mean of a contaminant is below a criterion or action level, and the MPE (maximum probable error) method for achieving a target precision around the mean, both following the NSW EPA sampling design guidelines.
Method references
US EPA QA/G-9 statistical guidance, MARSSIM, Gilbert (1987) Statistical Methods for Environmental Pollution Monitoring, and NSW EPA (2022) Sampling Design Part 1 - Application (publication 22p3915), Appendices E and F.