Measurement error

I'm aware that this is a very simple question, nevertheless I'd like to get some help.

I'm evaluating the precision of measuring angles in a certain experiment - the object lies in a Petri dish under a certain angle to the 'north' position. I have measured the photo of the object 15 times during different 15 days, so I have 15 values (mean and median = 336.6 degrees) and range of measurement (335.5-337.0, i.e. 1.5 degree). Standard deviation of mean is 0.39 degree.

My question is, do I understand correctly that the error of measurement will be (SD/mean)*100% (i.e. 0.11%), and not (1/2*range/mean)*100% (i.e. 0.22%)?

Thank you.


TS Contributor
It is not as simple as you think. Measurement error means different things in different disciplines. For example, in my discipline (industrial statistics), measurement error can be decomposed into:
  • Accuracy
    • Bias
    • Linearity
    • Stability
  • Precision
    • Repeatability
    • Reproducibility
With your data, you could potentially assess bias, stability and repeatability. In other disciplines, the answer will likely differ.


TS Contributor
Your formula is the coefficient of variation converted to a percentage. It would be one approach for assessing repeatability of a measurement. However, it is not used in my discipline, so I cannot comment on its relative merits or flaws.
Thank you. I see that I have to consult literature on measurement errors in life sciences.
If anyone can provide references to valuable sources on this topic, I would very much appreciate this.