Comparison of solar-neutrino signals in SNO ( ( 1 ) ) and Super-Kamiokande ( SK ) ( ( 2 ) ) detectors results in discovery of \nu _ { e } \rightarrow \nu _ { \mu, \tau } oscillations at level 3.1 - 3.3 \sigma ( ( 1 ) ) .
This comparison involves the assumption of neutrino spectrum and a choice for the thresholds of detection in both experiments .
In this Letter we obtain an exact formula for the comparison of the signals which is valid for arbitrary spectra and thresholds .
We find that the no-oscillation hypothesis is excluded at 3.3 \sigma .
If the energy-dependent component of the survival probability for electron neutrinos is small as compared with the average value , i.e .
in the case of small distortion of the observed spectrum , the oscillation hypothesis can also be tested to similar accuracy .
The oscillation to sterile neutrino only , is excluded at 3.3 \sigma level , and oscillation to active neutrinos is confirmed at the same level , though with some reservations .