  Vertical test is a commonly used experimental method to qualify
Superconducting Radio Frequency (SRF) cavities. Taking the experiences at
Jefferson Lab (JLab) in US for example, over thousand of vertical tests have
been performed on over 500 different cavities up to now [1]. Most of the tests
at JLab followed the method as described in [1], but all the uncertainties of
the calculated quality factors as well as the gradients were in-accurate due to
the wrong algorithm used. In this paper, a first-principle method was applied
to analyze the uncertainty of the data, and the results were compared with
those in [1] under typical experiment conditions.
