Calculating the One-Sided 90% Upper Confidence Limit of the Mean

The Environmental Protection Agency offers a spreadsheet to calculate the 90% upper confidence limit of the arithmetic mean of simple data sets. The 90% UCL is often used to represent the average exposure to contaminants for purposes of calculating risk at a contaminated site.

The UCL spreadsheet software was developed by EPA’s Technical Support Center and is used by Oregon Department of Environmental Quality staff. The program is offered by EPA for use without guarantees or support. The Department may decide to use UCLs other than those generated by ProUCL.

More information about the spreadsheet and the ProUCL 5.1.00 software can be viewed and downloaded from:

Technical Support Center for Monitoring and Site Characterization
Statistical Software ProUCL 5.1.00 for Environmental Applications For Data Sets with and without Nondetect Observations