Comparison between the flux variability in optical and X-rays as in Fig. 2, for disk-bearing stars whose optical variability has been classified by Cody et al. (2014). “Burster”, “unclassified”, “not variable”, “quasi-periodic”, “long term variable”, and “multi-periodic” stars are marked with filled dots (red for the “bursters” and black for the remainder), while “stochastic” stars are marked with green × symbols and “dipper” stars with blue squares. In the upper left corner of each panel we show the probabilities derived from the correlation tests using both the entire sample and the dippers+stochastic stars (the latter inside brackets).