Differences Among Experts Regarding the Expression of Measurement Uncertainty

Confusion with terminology

Drawing conclusions from experimental data is the foundation of physics

Different conventions are used to report measurement uncertainties

What is the meaning of ± 5 inm = 75 ± 5 g ?

Measurement uncertainty experts

Different standards for x ± ?x based on expert opinions:

Do these measurements agree?x = 20 ± 5, y = 30 ± 5

Do these measurements agree? x = 30 (?x= 1), y = 40 (?y= 5)

Are these exam averages different? A = 70 ± 15, B = 76 ± 14 (N = 50 students)

But if we consider the standard error: A = 70 ± 2, B = 76 ± 2

Suppose that a voter-exit poll finds candidate A is favored over B with a 53% majority (± 4% margin of error).

Assuming margin of error is ± 1?:

Survey polls typically report a 95% confidence level (± 2?)

Conclusion from poll vote:

PPT Slide

ISO Guide, p.7

ISO recommended practice:Avoid ± notation and explain clearly.

How many significant figures?

“Remember to include units!”

Email: Duane_Deardorff@ncsu.edu

Home Page: www.ncsu.edu/PER

Other information: APS Centennial Mtg, March 99, Atlanta