The primary goal of the Kepler mission is to determine the frequency of Earth-size planets in the habitable zones of solar-like stars. The mission has published a catalogue of planet candidates, but there are two key attributes of the catalogue that we need to understand before we can determine the underlying planet population - the rate of false negatives (completeness) and the rate of false positives (reliability). I will discuss our efforts towards determining the completeness of the survey, in particular characterising the behaviour of the automated transit detection software.