There are several methods in WIMS to calculate Method Detection Limits (MDL).  The EPA defines the MDL as the "minimum concentration of substance that can be measured and reported with 99% confidence that the analyte concentration is greater than zero, and is determined from analysis of a sample in a given matrix containing the analyte".

The basic calculation when using the default of 7 replicates is:

3.143 * Standard Deviation of Replicates.

T Values (3.143 in above example) for different number of replicates:

Number of Replicates	Degrees of Freedom	T Value
7	6	3.143
8	7	2.998
9	8	2.896
10	9	2.821
11	10	2.764

WIMS Methods:

1. Use the Custom Data Entry Template MDL-Calculator found in Miscellaneous Custom Data Entry Form Templates.  This template works will when you run the replicates in one day and simply want to enter the data and have the MDL calculated.  Also, does the 5 Point Check of the MDL Calculation.

2. If the replicate data is entered into a variable.  Design a report to find the date of the 6th previous value using the DLV function.  The use the Spread Function GDEV referring to the current date and the date returned by the DLV function:

Download Example Template: HelpMDLCalc.hwr (Click here for download instructions)

3. Use the MDL Study Form in Lab Cal