Studies across a broad range of disciplines–from psychiatry to cognitive science to behavioral neuroscience–have reported on whether the magnitude of contrast sensitivity alterations in one group or condition varies with spatial frequency. Significant interactions have often gone unexplained or have been used to argue for impairments in specific processing streams. Here, we show that interactions with spatial frequency may need to be re-evaluated if the inherent skew/heteroscedasticity was not taken into account or if refractive error could plausibly differ across groups or conditions. By re-analyzing a publicly available data set, we show that–when using raw contrast sensitivity data–schizophrenia patients exhibit an apparent contrast sensitivity impairment at low, but not high, spatial frequencies, but that when using log-transformed data or when using generalized estimating equations, this interaction reversed. The reversed interaction, but not the overall contrast sensitivity deficit, would disappear if groups were matched on visual acuity. However, matching groups in this way is probably only defensible if acuity differences arise from optical blur. These analyses reconcile seemingly discrepant findings in the literature and demonstrate that properly reporting contrast sensitivity interactions with spatial frequency requires accounting for refraction error and skew/heteroscedasticity.