Estimating the Probability of High Microbial Counts Using Excel*

Current version: February 18, 2013

For more information see: Peleg, M. 2006. Advanced quantitative microbiology for food and biosystems: Models for predicting growth and inactivation. CRC Press, Boca Raton FL. Download a .PDF file (452K) containing the book's table of contents and an order form.

An Excel worksheet is used to estimate the probability of an unusually high microbial count from a past time series of fluctuating counts assuming the data in that series have a normal or lognormal distribution.

The pop-up comment notes from the worksheet are also available on this page so that you may read and/or print them before using the worksheet.

Version 7 makes some corrections to the comment notes attached to cells A4, A12 and A20. It also includes the previous version 6 correlation coefficient calculations and Quantile-Quantile plots to help decide whether the data are normally or lognormally distributed. An 'Update Worksheet' button runs a Visual Basic macro to automatically update any cells and charts in the worksheet that are affected by changes in the microbial count data. You must click on the 'Enable Macros' button in the dialog box that is displayed before the worksheet opens in Excel in order for the macro to be useable.

* Excel® is a registered trademark of Microsoft Corporation. You can get more information about Excel by visiting Microsoft's web site at:

Download the Demonstration Excel Worksheet File

The Excel worksheet (MicrobialCountProbability.xls) is available in the file format of Excel 97 through 2007 for Windows and Excel 98 through 2004 for MacOS. If you have a modern web browser you should be able to download the binary Excel file directly by clicking on the link below. If a compatible version of Excel is currently installed on your computer, double-click the icon for the MicrobialCountProbability.xls file that was downloaded to open the worksheet in Excel. Be sure to click the 'Enable Macros' button in the dialog box that appears. If you are using a recent version of Excel for Windows, you may need to first reduce the security level in Tools>Macro>Security to Medium, then close and reopen the file to enable the macros.

For Windows and MacOS:
Excel binary file (590K) for Windows Excel 97 through 2007 and MacOS Excel 98 through 2004: MicrobialCountProbability.xls

This page has been visited ********* times since November 6, 2000.

[Return to ] Free Microsoft Excel Workbook Software

[Return to ] Prof. Micha Peleg

[Return to ] Mark D. Normand

[Return to ] UMass Department of Food Science

[Return to ] University of Massachusetts at Amherst

Content last updated: February 18, 2013