This week in school, there is a 75 percent probability of having a fire drill, a 50 percent probability of a tornado drill, and a 25 percent probability of having both drills. let event f be a fire drill and event t be a tornado drill. are the two events independent? no, because p(f ∩ t) ≠ p(f) • p(t). no, because p(f ∩ t) ≠ p(f) + p(t). yes, because p(f ∩ t) = p(f) • p(t). yes, because p(f) = p(t) + p(f ∩ t).