Risk factor If the factor is present the effect will always occur (If a person smokes cigarettes, they will get lung cancer) The factor must be present for the effect to occur (People only get lung cancer from smoking cigarettes) If the variable is present, the probability that the effect will occur is increased Sufficiency O If the factor is present the effect will always occur (If a person smokes cigarettes, they will get lung cancer) The factor must be present for the effect to occur (People only get lung cancer from smoking cigarettes) If the factor is present, the probability that the effect will occur is increased