Inductive ballasts will light the bulbs 120 times a second, electronic ballasts will light them around 22,000 times a second as a rule. So it's relatively trivial to figure out which kind you have, just get some shiny cylindrical object and move it very quickly through your field of view under the lamp's illumination, and if it traces stripes through the air, you've got an inductive ballast, if the trace appears smooth, it's electronic.
