# Qeustion on formulation

1. May 16, 2010

### Niles

1. The problem statement, all variables and given/known data
Hi

Say I have measured the mass of 2 particles, and I find

m1=0.552 kg
m2=0.556 kg.

I would like to say that the masses are equal up to 0.55. Is it proper to say "they are equal up to the third digit"?

Sincerely,
Niles.

2. May 17, 2010

### kuruman

It would be more proper to find the percent difference, x. If your measurement is accurate to a number greater than x percent, then you can say "The masses are equal to within the accuracy of the experiment." Otherwise you cannot. In short, you have to do some error analysis.

3. May 17, 2010

### Niles

The thing is, I am doing all of this numerically - but one system is larger than the other (i.e. more data points), so the result I get should - in principle - have converged more. The good news is that I get the same answer, which means that my original measurements (the "small" system) are correct.

4. May 17, 2010

### kuruman

I am not sure what you mean by "numerically". Where did you get the numbers? Were they just given to you, or were they the results of numerically processed data from an experiment that you conducted? If you have performed an experiment, then you should have a feeling of its percent accuracy.

5. May 17, 2010

### Niles

They are numbers that I was given - I think they just describe realistic systems, not necessarily real systems.

6. May 17, 2010

### kuruman

Then all you can say is that "the masses are equal to within x percent".

7. May 17, 2010

### Niles

Just to be 100% clear: So if I get e.g. m = 0.10 kg and m=0.11 kg, then they are the same to within 10%?

8. May 17, 2010

Correct.