# How is this procedure of error propagation called?

I'm calculating the error on $\theta$ from given PDG values for $f(\theta)=sin^2(2\theta) \pm \sigma_{f}$

Question: I'd like to calculate the errors (from the inverse function) as $$\sigma_{\theta}^{neg} = f - f^{-1}( f - \sigma_{f}^{neg} )$$ $$\sigma_{\theta}^{pos} = f^{-1}( f + \sigma_{f}^{pos} ) - f$$

How is this procedure called officially? Does it have a commonly understood name?

I found here the name "(e) [...] The simple approach.", which does not sound descriptive of the procedure.

Comment: I'm not sure about the Gaussian error propagation in this case, since the error is asymmetric and the Gaussian approximation - which only gives a slope of the function at this point - does not describe the confidence interval well.

• I think this question is more suitable for mathematics forum. – hsinghal Jul 2 '16 at 18:35
• I'm asking for a field-specific term, so the forum is fitting. – IljaBek Jul 2 '16 at 22:53