measurment-uncertainty

measurment-uncertainty - University of Florida Mechanical...

Info iconThis preview shows pages 1–6. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: University of Florida Mechanical and Aerospace Engineering 1 Useful Tips for Presenting Data and Measurement Uncertainty Analysis Ben Smarslok University of Florida Mechanical and Aerospace Engineering 2 Outline • Why is presenting data properly important? • Explain important terminology and definitions – NIST vs. ISO vs. ASME/ASTM – Oberkampf definitions of model uncertainty (not included) • Experimental scenarios and corresponding methods – Uncertainty propagation – Crossed vs. nested factors (ANOVA vs. VCA) – p-values – Interlaboratory Studies (not included) University of Florida Mechanical and Aerospace Engineering 3 • Best guess by experimenter • Half the smallest division of measurement • Standard deviation: σ • Standard error: σ m = σ / √ n • Expanded uncertainty of ± 2 σ or ± 3 σ (95% or 99% confidence interval) • Standard uncertainty: u • Combined standard uncertainty: u c *(Courtesy of Duane Deardorff presentation from UNC) m = 75 ± 5 g What is the meaning of ± 5 ? University of Florida Mechanical and Aerospace Engineering 4 What does x ± u mean? • Engineers think in terms of ±2 σ (95%) • Physicists generally report ±1 σ (68% CI) • Chemists report ±2 σ or ±3 σ (95% or 99% CI) • Survey/poll margin of error is 95% CI • Accuracy tolerances are often 95% or 99% • NIST Calibration certificate is usually 99% • Conclusion : The interpretation of ± u is not consistent within a field, let alone between fields – It is very important to explain the statistical relevance of the uncertainty bounds!!! University of Florida Mechanical and Aerospace Engineering 5 Presenting Uncertainty Precisely • Choose a standard for presenting uncertainty (I prefer NIST), and reference the standard • Explain the source of the uncertainty – Type A – calculated by statistical methods (it is useful to explain the design of experiments and the number of samples involved) – Type B – determined by other means, such as estimate from experience or manufacturers specifications • Use terms carefully!...
View Full Document

This note was uploaded on 06/06/2011 for the course EAS 4240 taught by Professor Peterifju during the Spring '08 term at University of Florida.

Page1 / 17

measurment-uncertainty - University of Florida Mechanical...

This preview shows document pages 1 - 6. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online