Correlation plot between N_cry/N_all and N_pyr/N_all and their histograms. Filled and open black squares show the objects whose 5.3–12 μm spectral fits are accepted and those rejected on the basis of the χ² statistics with a significance level of 0.05, respectively. Black and white bars in the histograms also indicate the sources in which the spectral fits are accepted and rejected, respectively. The correlation coefficient and the p-value for the accepted sample are shown at the bottom right corner of the correlation plot. Red diamond and dotted lines show the silicate dust properties obtained from the Sgr A* spectrum, a typical spectrum of the diffuse ISM in our Galaxy (Kemper et al. 2004).