Are different methods required for comparison to ACLs and MCLs?
When comparing measurements to a standard, the same approach is used (e.g., a 95% upper confidence limit for the mean of the last four measurements) regardless of how the standard was derived. • If I have constituents with detection frequencies less than 25% for intra-well or less than 50% for inter-well comparisons do I have to wait until I have a minimum of 13 background samples before I begin computing statistics? No. For inter-well comparisons remember that the number of background samples is pooled over all upgradient wells so with eight samples in each of two wells you have 16 background samples. For intra-well comparisons 13 background samples are required for a nonparametric prediction limit with one verification resample but only eight background samples are required with two verification resamples (i.e. fail the first and pass either one of two verification resamples). Alternatively, Poisson prediction limits can be used with as few as four background samples regardless of de
