You cannot determine how likely something is to occur in a universal sense. To be accurate, the headline should read "young drivers who fail test 20% more likel

You cannot determine how likely something is to occur in a universal sense. To be accurate, the headline should read "young drivers who fail test 20% more likely to be in crash than those who pass". As it stands, this reads like an advertisement for a test you can give your teen to decide whether or not they should be allowed to drive. A 20% improvement in predictive power is not worth the money, since it probably shouldn't change your decision.