Using the empirical relationship between BAC and self-reported volume (VSR), a continuous empirical volume estimate (V^E) was produced from each BAC by inverting the empirical relationship. Similarly, for each BAC a Widmark-estimated volume (V^W) was produced by inverting the Widmark equation for the volume consumed. In order to simplify the display of the results for the various volume measures, volume bins (or grouped continuous ranges of volume) were defined for 1, 2, 3–4, 5–7, 8–9, and 10+ drinks for each of the 3 measures (VSR, V^E, and V^W). For example, the volume bin for 1 drink was the volume range from 0 to 1.5 drinks; for 2 drinks the volume range was 1.51–2.5 drinks, etc. Measures of the agreement between VSR (the self-reported volume of consumption) and V^E as well as between VSR and V^W were estimated for the continuous underlying measures using Pearson’s correlations. For the corresponding binned volume variables, a weighted Cohen’s κ was estimated.
