August 18th, 2021

The tool you choose depends on the intended use.

A Bit More About Relative Bias

In my last post I introduced the concept of relative bias. I wrote that unless there is a reference standard against which a measurement can be compared, only relative bias – the difference between test results obtained by different methods – can be assessed. In my example, I compared the results of two test methods for determining the concentration of end-use diluted metalworking fluids (MWF). …


July 29th, 2021

The tool you choose depends on the intended use.


Culture Versus Non-Culture Test Methods


There is a false impression among microbiologists and non-microbiologists alike that because culture testing has been around since the mid-19th century, it is a reference method (I’m come back to the reference method concept in a bit). The first quantitative culture-based method – the heterotrophic plate count (HPC) first appeared in Standard Methods for the Examination of…


June 24th, 2021


In my March 2021 article, I began a discussion of root cause analysis (RCA). In that article I reviewed the importance of defining the problem clearly, precisely, and accurately; and using brainstorming tools to identify cause and effect networks or paths. Starting with my April 2021 article I used a case study to illustrate the basic RCA process steps. That post focused on defining current knowledge and defining knowledge gaps. Last month, I covered the next two steps: closing…


May 19th, 2021

Former U.S. Secretary of Defense Donald Rumsfeld statement from 12 February 2002, Department of Defense news briefing.

RCA Universal Concepts

Before discussing RCA’s fifth and sixth steps I’ll again share the figure I include with my April article. Successful RCA includes eight primary elements. Figure 1 illustrates the primary RCA process steps, with Steps 5 & 6 highlighted.

Fig 1. Common elements shared by effective RCA processes.

Steps 1 through 4 Refresher:…


April 30th, 2021

Today’s ASM News Digest reported that on 04 April, Thomas D. (Tom) Brock passed away at the age of 94 (Microbiologist Thomas Brock Dies at 94 | The Scientist Magazine® ( This week there was also a column about him in the New York Times (Thomas Brock, Whose Discovery Paved the Way for PCR Tests, Dies at 94 – The New York Times (  Here I’ll share my personal story.

Although Tom spent most of his career as a professor at the University of…



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