Writing the Perfect Method!
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Part 10: Calculations and Reporting
As we finish up this series on the perfect method, we want to cover the last main issues – how to calculate results, and what numbers to put in your report. Like every other topic that we have discussed, these are just as important as the rest. A poorly written section here could result in wasted time or incorrect results.
Calculations
I was reading a method recently because I was asked to create a new report template to replace the current spreadsheet. There were several equations listed, using a mixture of written descriptions and abbreviations. Some made sense; some did not. I could not find definitions for some of the abbreviations, so it was not always clear how to actually calculate the results. An example spreadsheet printout was available, but was no help, because the labels did not match the names in the method. Despite looking over the method for about 10 minutes, I still had no idea how to duplicate the calculations. Studying the formulas in the actual spreadsheet file would be the only way to duplicate the results.
Reporting
For most people outside the lab, the purpose of the lab is to generate numbers – numbers in a report. We might imagine that we are actually generating “data” or “information,” but most readers of our reports will have no idea how we got the results, and they will rarely appreciate how much skill and effort that it requires. Still, this is what we do, so we need to do it the right way.
The purpose of your report is to communicate results to the user.
But, remember that results are more than just a number from the spreadsheet. You are also communicating information about how “good” this number is – does it reflect an estimate of a trace level analysis, or is it an accurate and precise value to be used in a certificate of analysis or manufacturing release document. Does this number indicate whether it comes from a single measurement or multiple replicates? I there any indication of the variability in the number? That is, can I estimate if two numbers are essentially the same? Will the reader be able to answer any of these questions?
For Calculations and Reporting sections,
Do:
- Define all abbreviations and acronyms
- Include the units for all numbers, either individually, or in the column header
- Show example calculations
- Report the proper number of significant figures. Most chromatographic methods will generate two or three significant figures. Your method should specify the number of significant figures, or the decimal level for reporting (e.g., report to the first decimal place). If you are not sure, consider reviewing our free on-line course on Significant Figures and Rounding.
- For more than two replicate measurements, you must report the average, standard deviations, and the number of data points used to calculate the values. Without the number of data points, the standard deviation will have no real meaning. For more information, consider ordering our seminar on Analytical Lab Techniques, which also includes sections on other lab skills.
Do Not:
- Assume that the reader knows abbreviations or can “figure them out.”
- Forget the units. The reader should know the units for every number in the report.
- Copy values from a spreadsheet without considering significant figures.
- Assume the user will understand the variability of the method and therefore know how to interpret the numbers.
Next Month: Special Topics and User Questions
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Register for Our Seminars at Eastern Analytical Symposium
November 16 - 18, 2014
Somerset, NJ
Register for an EAS Short Course
Troubleshooting Chromatographic Systems
November 16 - 17
Learn about proper peak integration as well as complete coverage of LC and GC troubleshooting. Bring in your own examples for discussion.
Sample Preparation: The Chemistry Behind the Techniques
November 18
This one day workshop provide a complete overview of sample preparation principles and techniques. The discussion includes many real-world examples for discussion. This is one of the longest-running classes at EAS. We have trained hundreds of analysts over the last 20 years. Come join us.
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Quote for the Day
"People, including managers, do not live by pie charts alone — or by bar graphs or three inch statistical appendices to 300 page reports. People live, reason, and are moved by symbols and stories."
– Tom Peters,
Thriving on Chaos, Knopf, 1987. |
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Dowload Recent Presentations
Get your own copy of two recent presentations. Both cover our recent work on HILIC columns. These publications describe a simple way to evaluate multi-mode mechanisms on HILIC columns.
Pittcon, March, 2014:
Mixed Mode Mechanisms in LC: Curse or Cure?
Minnesota Chromatography Forum, May, 2014:
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ACCTA, Inc.
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