Abstract: We discuss oscillations of atmospheric and solar neutrinos into sterile neutrinos in the 2+2 scheme. A zeroth order sum rule requires equal probabilities for oscillation into nu_s and nu_tau in the solar+atmospheric data sample. Data does not favor this claim. Here we use scatter plots to assess corrections to the zeroth order sum rule when (i) the 4 x 4 neutrino mixing matrix assumes its full range of allowed values, and (ii) matter effects are included. We find that the sum rule is significantly relaxed. This weakens the case against the 2+2 model and the sterile neutrino. To invalidate the 2+2 model, a global fit to data with the small mixing angles included, or a miniBooNE result, seems to be required.