Histograms of the background subtracted radio flux for all of the associated events that showed interplanetary type III bursts (red) and did not show interplanetary bursts (blue). The radio frequencies shown are 164+173 MHz with 109 and 49 events for IT3s and no IT3s, respectively (top left), 237+228 MHz with 103 and 54 events (top right), 327 MHz with 73 and 46 events (bottom left) and 411+408 MHz with 49 and 36 events (bottom right). All the events had at least 1.5 times the background radio flux.