Land's Formula Confidence Interval (calculation from background)

(Background to Compliance Comparison)


For Log-Transformed Data

 

See Also:

Upper Confidence Limit (UCL) Comparisons

Land's Formula MCL Confidence Interval

Parametric Confidence Interval MCL Test

 

Description:

 

The Land's Formula UCL Method is a lognormal test for calculation upper, lower, and two-tailed confidence limits from measured sample concentrations.

 

This method follows the implementation described in both:

 

  • USEPA statistical guidance document "Calculating Upper Confidence Limits for Exposure Point Concentrations at Hazardous Waste Sites."

 

  • Gilbert (1987) page 170.

 

This method does not use MCLs or ACLs.

 

 

Use:

 

Use the Land's Formula UCL Method to calculate a 95% upper confidence limit from a collection of sample of environmental media collected at the site. The UCL is only calculated from sampling points listed as background. Compliance samples are not required, but if compliance samples do exists, each compliance sample concentration will be compared to the UCL. A statistically significant increase is indicated if the compliance sample concentration exceeds the UCL.

 

For this analysis, ChemStat supports upper and lower confidence limits at the 95% confidence level, and two-tailed limits at the 90% confidence level.

 

 

Remarks:

 

The method is designed for CERCLA compliant sampling programs. Unlike RCRA sampling which typically monitors the same sampling points for an extended period of time, this method is suitable for collections of samples taken at one point in time, but from many locations at the regulated site.