  To have a better understanding of a physical process, a comparison of
ex-perimental data with theoretical values is mandatory. The comparison
ismeaningful if the uncertainty in the experiment is accounted well. However,it
is seldom seen, especially for a complex phenomenon. We take a test casethrough
L subshell ionization of atoms by particle impact. Experimentally,x-ray
production cross-sections are measured, but ionization cross-sectionsare
calculated theoretically. Furthermore, the uncertainty of the x-ray pro-duction
cross-section is mainly statistics and detector-efficiency driven.
Butionization cross-section involves many other factors because of the
relation-ship between the production and ionization cross section, having wide
uncer-tainty spectrum. Consequently, determining the measurement uncertainty
inL subshell ionization cross-section is always difficult. We have studied
thisissue in the simplest way, where the rule of weighted propagation of
rela-tive uncertainty is utilised. We notice that larger uncertainties are
involvedin atomic parameters relevant to L1(2s1/2) subshell than those
associatedwith the other two L2(2p1/2) and L3(2p3/2) subshells. Hence,
comparisonbetween theory and experiment would give higher emphasis
onL2andL3subshell ionization cross sections. We believe this work aware us that
theappropriate uncertainty evaluation is extremely important for providing
theright judgment on the data.
