How Do You Determine if Two Values Agree?

[GrahamCU]

SOLVED:Agreement of 2 values

This is my first post, so I hope this is the write section for it..

How do you check if 2 values agree with each other (I've seen it called the "comparison test", but I can't find what I'm looking for by google-ing that).

For example, you have

x1=563+-12
x2=545+-38

And you have to find the "ratio". The values are said to agree if R<2 and disagree if R>2

Thanks,
Graham



EDIT: found the answer

R=(x1-x2)/root(sigmax1^2 + sigmax2^2)

 

[tiny-tim]

Welcome to PF!

Hi Graham!

Glad you sorted it out!

Anyway, welcome to PF …

and here's a square-root: √ and a plus-or-minus: ± and a sigma: σ for you. ​

 

[thomate1]

I would approach this question by first defining what is meant by "agreement" between two values. In this case, it seems that the ratio of the difference between the two values to the uncertainty (expressed as the square root of the sum of the individual uncertainties squared) should be less than 2 for the values to be considered in agreement. This makes sense, as a difference within the range of uncertainty can be considered acceptable.

To check if two values agree, we can calculate the ratio R using the formula provided in the edited post. If R is less than 2, then the values are in agreement. If R is greater than 2, then they are considered to disagree.

It is important to note that this approach assumes that the uncertainties are normally distributed, and that the values being compared are independent of each other. If these assumptions do not hold, alternative methods may need to be used to determine agreement between the values.

In addition, it is always good practice to include the uncertainties in any reported values to accurately convey the level of agreement between measurements.