Band strength ratios, I, versus EW₅₇₉₇/EW₅₇₈₀ for four different DIB pairs. In panels 9a and 9b, there is a positive correlation, but d(Q, S) remains similar for ζ and σ sight lines. Panel 9c shows variation in I, but weaker correlation with EW₅₇₉₇/EW₅₇₈₀. Consequently, the 4984 Å DIB more likely shares a common carrier with the 5512 Å DIB than the 4963 Å one. In panel 9d, d(Q, S) decreases for ζ sight lines, contrary to all other pairs. Measurement errors of I can be estimated via the spread of measurements for a single sight line; that is, for one single EW₅₇₉₇/EW₅₇₈₀ value.