Quality Progress - July 2016 - (Page 47)

MEASURE FOR MEASURE BY ELIZABETH J. GENTRY AND GEORGIA L. HARRIS Write It Right Understanding nuances of metrics in technical writing Editor's note: This is part two of a academics. Appendix B provides round- and their sources. Conversion calcula- two-part series exploring accuracy in ing guidance and unit-conversion factors tions require rigorous software valida- measurement results. Part one appeared for a broad set of measurement units. tion, which is a time-consuming process. in May 2016's QP. NIST published several similar technical At best, conversion-calculation errors guides, including the Metric Style Guide can cause expensive mistakes. At worst, MANY QUESTIONS ARISE while for the News Media, which provides their consequences can be a matter of you're writing laboratory documents, condensed SI content to highlight com- life and death. clarifying measurement results or monly used measurement information.3 A implementing measurement system best convenient hub of SI style guidance also Ground control to accuracy practices. The proper use of measure- is available on the NIST metric program's The 1999 crash of NASA's $125 million ment units and symbols in laboratory website. NASA Mars climate orbital spacecraft documents-such as calibration reports, 4 Use a leading zero: For numbers served as a wake-up call for potential control charts, uncertainty tables or less than one, a zero is written before errors related to working with multiple standard operating procedures-is criti- the decimal point.5 This ensures a measurement systems. The mishap oc- cal to effectively communicate technical quantity is appropriately interpreted curred because the spacecraft entered information. The National Institute of Standards and Technology (NIST) was delegated the responsibility to interpret or modify the International System of Units (SI, also known as the metric system) for use in the United States. To accomplish this, NIST provides several SI resources to support sectors of science, technology, trade and commerce. It also serves as the U.S. technical representative to " the Mars atmosphere on a trajectory that There are many resources that can help you avoid being responsible for inaccuracies in measurement reporting. " was too low.6 NASA later identified the root cause of the erroneous trajectory and velocity calculations: A contractor failed to use SI units of force (Newton, or N) as specified by NASA in the coding of a ground software file used in trajectory models. One corrective action that NASA recommended was to perform software audits to evaluate specification compliance on the International Bureau of Weights and and helps avoid consequences of a mis- all data transferred between NASA and Measures (BIPM) that defines the SI. placed decimal point. Without a leading the contractor.7 These publications are used to guide the zero, a value like .25, for example, could measurement unit style in technical and be misinterpreted as 25, an error that Language arts documentary standards. makes it 100 times greater in magni- Several helpful conversion-factor resourc- tude. Such an error could seriously es have been made available on the NIST and NIST SP 811 provide the legal inter- harm a patient if the quantity represent- metric program's website.8 Caution is rec- pretation of and guidelines for SI use in ed a medication dose. ommended to organizations developing NIST Special Publication (SP) 330 the United States. NIST SP 811 also pro- Avoid unit-conversion errors: unit-conversion software or using online vides detailed rules for SI writing style, Using the SI reduces the number of calculators for technical purposes. It's including a useful editorial checklist.1, 2 errors associated with measurement important to conduct a rigorous valida- conversions between U.S. customary tion and verification analysis before using Striving for zero errors units and the SI. Eliminating conversions unit-conversion software. NIST SP 811 is written for technical audi- altogether negates the need to document ences, such as engineers, scientists and which conversion factors are being used Spelling and pronunciation of measurement units-This can be July 2016 * QP 47

Table of Contents for the Digital Edition of Quality Progress - July 2016

Up Front
LogOn
Expert Answers
Keeping Current
Mr. Pareto Head
A Quick Study
Clear Pathway
Pulling It All Together
Dead or Alive
Innovation Imperative
Measure for Measure
Quality in the First Person
Career Corner
Standards Outlook
ASQ's Continuing Education and Profesional Development Directory
QP Toolbox
QP Reviews
One Good Idea
Back to Basics

Quality Progress - July 2016

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