Lognormal Fitting Utility Program: Extracting Parameters of Lognormal Distributions from a Column of Uncensored or Left-Censored Data

The Lognormal Fitting Utility Program, PWND-SA-7625, Version 2006-10-12.0, is a Microsoft(TM) Excel(TM) workbook that sorts a column of numerical data, assigns a fractile and standard normal deviate ('z-score') to each datum, takes the natural logs of the positive data, and computes various summary statistics. The methods are documented in Battelle-TIB-5000 (PNWD-3741 Rev. 0), sections 2.1.1 [ln(Data)] and 2.1.3. [Uniformly-weighted & Finney-weighted regressions] and were described to some extent by Strom (1986). The geometric mean is biased high if there were less-thans, zeroes, or censored data in the data range and only the ln(Data) were used, but is unbiased if only non-negative values occurred in the data set. The uniformly-weighted regression puts a line through the non-zero ln(Data) as a function of z.

The utility is useful for analyzing occupational monitoring data sets such as measurements of concentrations of radioactive materials in air in the workplace. One way to express the variability of such measurements is to describe them with a lognormal distribution. The parameters of the lognormal distribution are the geometric mean and geometric standard deviation. The variability of the data can be used to help characterize the uncertainty of doses inferred from them. Uncertainty is an important parameter in dose reconstruction such as is done for the Energy Employees Occupational Illness Compensation Program by the Office of Compensation Analysis and Support of the National Institute for Occuapational Safety and Health.

DISCLAIMER: Daniel J. Strom, Battelle, the Pacific Northwest National Laboratory, and the U.S. Department of Energy hereby disclaim any and all liability for any use or misuse of this software, and disclaim any and all liability for any errors in this software. USE AT YOUR OWN RISK.

Download the "Reusable" version and the "First Time" versions now; save them in some convenient folder. You must have Microsoft Excel to run the utility. The instructions are in a spreadsheet tab "Instructions." The "First Time" version permits you to save a useful chart format to your "Custom" "User defined" Excel charts that can be used later for any data set. The software goes slowly for more than a few hundred data points.

See also the LOGNORM4: Extracting Parameters of Lognormal Distributions from Minimal Information software page.

Reference

Strom DJ. 1986. "Estimating Individual and Collective Doses to Groups with 'Less than Detectable' Doses: A Method for Use in Epidemiologic Studies." Health Physics 51(4):437-445.

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